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The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate
field-effect transistor The field-effect transistor (FET) is a type of transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate ...
that is fabricated by the controlled oxidation of a
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
, typically
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
. The voltage of the covered gate determines the
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current An electric current is a stream of charged particle In p ...
of the device; this ability to change conductivity with the amount of applied voltage can be used for or switching electronic signals. The MOSFET was invented by
Mohamed M. Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physical chemist Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which ...

Mohamed M. Atalla
and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
at
Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories (1925–1984)) is an American industrial research and scientific development company A company, abbrev ...
in 1959, and first presented in 1960. It is the basic building block of modern electronics, and the most frequently manufactured device in history, with an estimated total of 13sextillion () MOSFETs manufactured between 1960 and 2018. It is the dominant
semiconductor device A device is an that relies on the properties of a material (primarily , , and , as well as s) for its function. Semiconductor devices have replaced s in most applications. They in the , rather than as free electrons across a (typically l ...
in
digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Electronics comprises the physics, engineering, technology a ...
and analog
integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indivi ...

integrated circuits
(ICs), and the most common
power device A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics (for example in a switch-mode power supply). Such a device is also called a power device or, when used in an integrated circuit, a power IC. A ...
. It is a compact
transistor upright=1.4, gate Candi bentar, a typical Indonesian gate that is often found on the islands of Java">Indonesia.html" ;"title="Candi bentar, a typical Indonesia">Candi bentar, a typical Indonesian gate that is often found on the islands o ...

transistor
that has been miniaturised and mass-produced for a wide range of applications, revolutionizing the
electronics industry The electronics industry is the economic sector that produces electronic devices. It emerged in the 20th century and is today one of the largest global industries. Contemporary society uses a vast array of electronic devices built in automated or s ...
and the world economy, and being central to the
digital revolution The Digital Revolution (also known as the Third Industrial Revolution) is the shift from mechanical and analogue electronic technology Technology ("science of craft", from Ancient Greek, Greek , ''techne'', "art, skill, cunning of hand"; ...
,
silicon age Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...
and
information age#REDIRECT Information Age The Information Age (also known as the Computer Age, Digital Age, or New Media Age) is a historical periodHuman history is commonly divided into three main Era, eras — Ancient history, Ancient, Post-classical history, ...
. MOSFET scaling and miniaturization has been driving the rapid exponential growth of electronic semiconductor technology since the 1960s, and enables high-density ICs such as
memory chip Semiconductor memory is a digital electronics, digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to MOS memory, where data is stored within metal–oxide–semiconductor (MOS) memo ...
s and
microprocessors A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circuitr ...
. The MOSFET is considered the "workhorse" of the electronics industry. A key advantage of a MOSFET is that it requires almost no input current to control the load current, when compared with
bipolar junction transistors A bipolar junction transistor (BJT) is a type of transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The ga ...
(BJTs). In an ''
enhancement mode Image:FET_comparison.png, Depletion type FETs under typical voltages. JFET, poly-silicon MOSFET, double-gate MOSFET, metal gate MOSFET, MESFET.  depletion ,  electrons ,  holes ,  metal ,  insulato ...
'' MOSFET, voltage applied to the gate terminal can increase the conductivity from the "normally off" state. In a ''
depletion mode Image:FET_comparison.png, Depletion type FETs under typical voltages. JFET, poly-silicon MOSFET, double-gate MOSFET, metal gate MOSFET, MESFET.  depletion ,  electrons ,  holes ,  metal ,  insulato ...
'' MOSFET, voltage applied at the gate can reduce the conductivity from the "normally on" state. MOSFETs are also capable of high scalability, with increasing
miniaturization Miniaturization ( Br.Eng.: ''Miniaturisation'') is the trend to manufacture ever smaller mechanical, optical and electronic products and devices. Examples include miniaturization of mobile phones A mobile phone, cellular phone, cell phone, ...
, and can be easily scaled down to smaller dimensions. They also have faster switching speed (ideal for digital signals), much smaller size, consume significantly less power, and allow much higher density (ideal for
large-scale integration An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit i ...
), compared to BJTs. MOSFETs are also cheaper and have relatively simple processing steps, resulting in high manufacturing yield. MOSFETs can either be manufactured as part of
MOS integrated circuit file:MOSFET Structure.png, upright=1.6, MOSFET, showing metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an gate oxide, insulating layer (pink). The metal–oxide–semiconductor field-eff ...
chips or as discrete MOSFET devices (such as a
power MOSFET A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS tr ...
), and can take the form of single-gate or
multi-gate A multigate device, multi-gate MOSFET or multi-gate field-effect transistor (MuGFET) refers to a metal–oxide–semiconductor field-effect transistor (MOSFET) that incorporates more than one gate into a single device. The multiple gates may be c ...
transistors. Since MOSFETs can be made with either p-type or n-type semiconductors ( PMOS or
NMOS logic N-type metal-oxide-semiconductor logic uses n-type (-) MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of ...
, respectively), complementary pairs of MOSFETs can be used to make switching circuits with very low
power consumption Electric energy consumption is the form of energy consumption Energy consumption is the amount of energy or power used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in ...
:
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
(Complementary MOS) logic. The name "metal–oxide–semiconductor" (MOS) typically refers to a
metal gate A metal gate, in the context of a lateral metal–oxide–semiconductor (MOS) stack, is the gate electrode separated by an oxide from the transistor's channel – the gate material is made from a metal. In most MOS transistors since about the mid 1 ...
, oxide insulation, and semiconductor (typically silicon). However, the "metal" in the name MOSFET is sometimes a misnomer, because the gate material can also be a layer of
polysilicon Polycrystalline silicon, or multicrystalline silicon, also called polysilicon or poly-Si, is a high purity, polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose const ...
(polycrystalline silicon). Along with
oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having vol ...
, different
dielectric In electromagnetism Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force i ...

dielectric
materials can also be used with the aim of obtaining strong channels with smaller applied voltages. The MOS capacitor is also part of the MOSFET structure. file:MOSFET functioning body.svg, upright=1.6, A cross-section through an nMOSFET when the gate voltage ''V''GS is below the threshold for making a conductive channel; there is little or no conduction between the drain and source terminals; the switch is off. When the gate is more positive, it attracts electrons, inducing an ''n''-type conductive channel in the substrate below the oxide, which allows electrons to flow between the ''n''-doped terminals; the switch is on. file:Threshold formation nowatermark.gif, upright=1.6, Simulation of formation of inversion channel (electron density) and attainment of threshold vol­tage (IV) in a nanowire MOSFET. Note:
threshold voltage The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals. It is an important scaling f ...
for this device lies around 0.45 V


Early history


Background

The basic principle of the
field-effect transistor The field-effect transistor (FET) is a type of transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate ...
(FET) was first proposed by Austrian physicist
Julius Edgar Lilienfeld Julius Edgar Lilienfeld (April 18, 1882 – August 28, 1963) was an Austro-Hungarian, and later American (where he moved in 1921) physicist and electrical engineer, who was credited with the first patent on the field-effect transistor The f ...
in 1926, when he filed the first
patent A patent is a type of intellectual property Intellectual property (IP) is a category of property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depe ...

patent
for an insulated-gate field-effect transistor.Lilienfeld, Julius Edgar (1926-10-08) "Method and apparatus for controlling electric currents" Over the course of next two years he described various FET structures. In his configuration, aluminum formed the metal and aluminum oxide the oxide, while
copper sulfideCopper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Eart ...
was used as a
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
. However, he was unable to build a practical working device. The FET concept was later also theorized by German engineer
Oskar Heil Oskar Heil (20 March 1908, in Langwieden – 15 May 1994, San Mateo, California San Mateo ( ; ) is a city in San Mateo County, California San Mateo County ( ), officially the County of San Mateo, is a county (United States), county located in ...

Oskar Heil
in the 1930s and American physicist
William Shockley William Bradford Shockley Jr. (February 13, 1910 – August 12, 1989) was an American physicist and inventor. He was the manager of a research group at Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell ...
in the 1940s. There was no working practical FET built at the time, and none of these early FET proposals involved thermally oxidized silicon. Semiconductor companies initially focused on
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
s (BJTs) in the early years of the
semiconductor industry The semiconductor industry is the aggregate of companies engaged in the design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process, or the result of that plan or ...
. However, the junction transistor was a relatively bulky device that was difficult to manufacture on a
mass-production Mass production, also known as flow production or continuous production, is the production of large amounts of standardized products in a constant flow, including and especially on assembly lines. Together with job production and batch product ...
basis, which limited it to a number of specialised applications. FETs were theorized as potential alternatives to junction transistors, but researchers were unable to build practical FETs, largely due to the troublesome surface state barrier that prevented the external
electric field An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particle In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' ' ...

electric field
from penetrating into the material. In the 1950s, researchers had largely given up on the FET concept, and instead focused on BJT technology. In 1955,
Carl Frosch Carl John Frosch (September 6, 1908 – May 18, 1984)Carl J Frosch (1908-1984)
Find A Grave was a ...
and Lincoln Derrick accidentally covered the surface of a silicon
wafer A wafer is a crisp, often sweet, very thin, flat, light and dry cookie, often used to decorate ice cream, and also used as a garnish on some sweet dishes. Wafers can also be made into cookies with cream flavoring sandwiched between them. They ...
with a layer of
silicon dioxide Silicon dioxide, also known as silica, is an oxide of rutile. Ti(IV) centers are grey; oxygen centers are red. Notice that oxygen forms three bonds to titanium and titanium forms six bonds to oxygen. An oxide () is a chemical compound that con ...
. In their subsequent experimental characterisation of this oxide layer they found that it blocked entry of particular dopants to the silicon wafer (despite allowing others) and thereby discovered the passivating effect of a surface
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...
layer on this semiconductor. Their further work demonstrated the etching of small openings into the oxide layer to diffuse dopants into precisely controlled areas of a silicon wafer. In 1957, they published a research paper and patented their technique summarizing their work. The technique they developed is known as oxide diffusion masking, which would later be used in the
fabrication Fabrication may refer to: * Manufacturing, specifically the crafting of individual parts as a solo product or as part of a larger combined product. Processes in arts, crafts and manufacturing *Semiconductor device fabrication, the process used to ...
of MOSFET devices. At Bell Labs, the importance of Frosch's technique was immediately realized since silicon oxides are much more stable than germanium oxides, have better dielectric properties and at the same time could be used as a diffusion mask. Results of their work circulated around Bell Labs in the form of BTL memos before being published in 1957. At
Shockley Semiconductor File:Facebook building 391, Mountain View, pre-dawn.jpg, Facebook's building 391, at the site of the Shockley Semiconductor Laboratory in Mountain View, California; pre-dawn view from the Hyatt Centric Hotel Shockley Semiconductor Laboratory was ...

Shockley Semiconductor
, Shockley had circulated the preprint of their article in December 1956 to all his senior staff, including
Jean HoerniJean Amédée Hoerni (September 26, 1924 – January 12, 1997) was a Swiss-American engineer. He was a silicon transistor pioneer, and a member of the " traitorous eight". He developed the planar process, an important technology for reliably fabr ...
.


Invention

Mohamed M. Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physical chemist Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which ...

Mohamed M. Atalla
at
Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories (1925–1984)) is an American industrial research and scientific development company A company, abbrev ...
was dealing with the problem of surface states in the late 1950s. He picked up Frosch's work on oxidation, attempting to passivate the surface of
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
through the formation of oxide layer over it. He thought that growing a very thin high quality thermally grown on top of a clean silicon wafer would neutralize surface states enough to make a practical working field-effect transistor. He wrote his findings in his BTL memos in 1957, before presenting his work at an
Electrochemical Society The Electrochemical Society is a learned society A learned society (; also known as a learned academy, scholarly society, or academic association) is an organization An organization, or organisation (English in the Commonwealth of Nati ...
meeting in 1958. This was an important development that enabled MOS technology and silicon
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
(IC) chips. The following year, John L. Moll described the MOS capacitor at
Stanford University Stanford University, officially Leland Stanford Junior University, is a private Private or privates may refer to: Music * "In Private "In Private" was the third single in a row to be a charting success for United Kingdom, British singer Du ...

Stanford University
. Atalla's co-workers J.R. Ligenza and W.G. Spitzer, who studied the mechanism of thermally grown oxides, managed to fabricate a high quality Si/ SiO2 stack, with Atalla and Kahng making use of their findings. The MOSFET was invented when Mohamed Atalla and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
successfully fabricated the first working MOSFET device in November 1959. The device is covered by two patents, each filed separately by Atalla and Kahng in March 1960. They published their results in June 1960, at the Solid-State Device Conference held at
Carnegie Mellon University Carnegie Mellon University (CMU) is a private Private or privates may refer to: Music * "In Private "In Private" was the third single in a row to be a charting success for United Kingdom, British singer Dusty Springfield, after an absence ...
. The same year, Atalla proposed the use of MOSFETs to build
MOS integrated circuit file:MOSFET Structure.png, upright=1.6, MOSFET, showing metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an gate oxide, insulating layer (pink). The metal–oxide–semiconductor field-eff ...
(MOS IC) chips, noting the MOSFET's ease of fabrication.


Commercialization

The advantage of the MOSFET was that it was relatively compact and easy to mass-produce compared to the competing planar junction transistor, but the MOSFET represented a radically new technology, the adoption of which would have required spurning the progress that Bell had made with the
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
(BJT). The MOSFET was also initially slower and less reliable than the BJT. In the early 1960s, MOS technology research programs were established by
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental pr ...
,
RCA Laboratories The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric General Electric Company (GE) is an American Multination ...
,
General Microelectronics General Microelectronics (GMe) was an American semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic copper ...
(led by former Fairchild engineer
Frank WanlassDr. Frank Marion Wanlass (May 17, 1933 in Thatcher, AZ – September 9, 2010 in Santa Clara, California California is a U.S. state, state in the Western United States. With over 39.3million residents across a total area of approximately ...
) and
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
. In 1962, Steve R. Hofstein and Fred P. Heiman at RCA built the first
MOS integrated circuit file:MOSFET Structure.png, upright=1.6, MOSFET, showing metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an gate oxide, insulating layer (pink). The metal–oxide–semiconductor field-eff ...
chip. The following year, they collected all previous works on FETs and gave a theory of operation of the MOSFET.
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
was developed by
Chih-Tang Sah Chih-Tang "Tom" Sah (; born in November 1932 in Beijing Beijing ( ), Chinese postal romanization, alternatively romanized as Peking ( ), is the Capital city, capital of the People's Republic of China. It is the world's List of national ca ...
and Frank Wanlass at Fairchild in 1963. The first CMOS integrated circuit was later built in 1968 by
Albert Medwin Albert H. Medwin (October 27, 1925 – October 26, 2020) was an American electrical engineer. He held several US patents, including ones in the field of electronic encoders. Medwin was involved in the early development of integrated circuits while ...
. The first formal public announcement of the MOSFET's existence as a potential technology was made in 1963. It was then first commercialized by General Microelectronics in May 1964, followed Fairchild in October 1964. GMe's first MOS contract was with
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agencies of the United States government, independent agency of the Federal government of the United States, U.S. federal government responsible for the civilian Li ...

NASA
, which used MOSFETs for
spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite alt=, A full-size model of the Earth observation satellite ERS 2 ">ERS_2.html" ;"title="Earth observation satellite ERS 2">Earth obse ...

spacecraft
and
satellites alt=, A full-size model of the Earth observation satellite ERS 2 ">ERS_2.html" ;"title="Earth observation satellite ERS 2">Earth observation satellite ERS 2 In the context of spaceflight, a satellite is an object that has been intentionally ...
in the
Interplanetary Monitoring PlatformInterplanetary Monitoring Platform was a program managed by the NASA Goddard Space Flight Center in Greenbelt, Maryland Greenbelt is a city in Prince George's County, Maryland, United States, and a suburb of Washington, D.C. Greenbelt is notable ...
(IMP) program and
Explorers Program The Explorers Program is a United States space exploration program that provides flight opportunities for physics, geophysics Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the ...
. The early MOSFETs commercialized by General Microelectronics and Fairchild were p-channel ( PMOS) devices for logic and switching applications. By the mid-1960s,
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric General Electric Company (GE) is an American Multination ...
were using MOSFETs in their consumer products, including
FM radio in Henderson, Nevada Henderson is a city in Clark County, Nevada Nevada (, ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, Calif ...
,
television Television, sometimes shortened to TV or telly, is a telecommunication Telecommunication is the transmission of information by various types of technologies over wire A wire is a single usually cylindrical A cylinder (from Gre ...

television
and
amplifiers An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power (physics), power of a Signal (information theory), signal (a time-varying voltage or Electric current, current). It is a two-port networ ...

amplifiers
. In 1967, Bell Labs researchers Robert Kerwin, Donald Klein and John Sarace developed the
self-aligned gate In electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic particles are ...
(silicon-gate) MOS transistor, which Fairchild researchers
Federico Faggin Federico Faggin (, ; born 1 December 1941) is an Italian-American physicist, engineer, inventor and entrepreneur. He is best known for designing the first commercial microprocessor, the Intel 4004. He led the Intel 4004, 4004 (MCS-4) project and ...

Federico Faggin
and Tom Klein adapted for
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
s in 1968.


MOS revolution

The development of the MOSFET led to a revolution in
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic particles are smaller than ...
technology, called the MOS revolution or MOSFET revolution, fuelling the technological and economic growth of the early
semiconductor industry The semiconductor industry is the aggregate of companies engaged in the design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process, or the result of that plan or ...
. The impact of the MOSFET became commercially significant from the late 1960s onwards. This led to a revolution in the
electronics industry The electronics industry is the economic sector that produces electronic devices. It emerged in the 20th century and is today one of the largest global industries. Contemporary society uses a vast array of electronic devices built in automated or s ...
, which has since impacted daily life in almost every way. The invention of the MOSFET has been cited as the birth of modern
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic particles are smaller than ...
and was central to the microcomputer revolution.


Importance

The MOSFET forms the basis of modern electronics, and is the basic element in most modern
electronic equipment Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electron The electron is a subatomic particle, symbol or , whose electric charge Electric charge is the physica ...
. It is the most common transistor in electronics, and the most widely used
semiconductor device A device is an that relies on the properties of a material (primarily , , and , as well as s) for its function. Semiconductor devices have replaced s in most applications. They in the , rather than as free electrons across a (typically l ...
in the world. It has been described as the "workhorse of the electronics industry" and "the base technology" of the late 20th to early 21st centuries.
MOSFET scaling The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor The field-effect trans ...
and
miniaturization Miniaturization ( Br.Eng.: ''Miniaturisation'') is the trend to manufacture ever smaller mechanical, optical and electronic products and devices. Examples include miniaturization of mobile phones A mobile phone, cellular phone, cell phone, ...
(see ''
List of semiconductor scale examples Listed are many semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how str ...
'') have been the primary factors behind the rapid exponential growth of electronic
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
technology since the 1960s, as the rapid miniaturization of MOSFETs has been largely responsible for the increasing
transistor density upright=1.4, gate File:Kebun Raya Bali Candi Bentar IMG 8794.jpg, Candi bentar, a typical Indonesian gate that is often found on the islands of Java and Bali A gate or gateway is a point of entry to or from a space enclosed by walls. The w ...
, increasing performance and decreasing
power consumption Electric energy consumption is the form of energy consumption Energy consumption is the amount of energy or power used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in ...
of
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
chips and electronic devices since the 1960s. MOSFETs are capable of high scalability (
Moore's law Moore's law is the observation that Transistor count, the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and Forecasting, projection of a historical trend. Rather than a ph ...
and
Dennard scalingDennard may refer to: People with the surname * Alfonzo Dennard, a professional American football cornerback, cousin to Darqueze * Amery Dennard, known as Big Herk, an American rapper * Brazeal Dennard, an American singer and educator * Darqueze ...
), with increasing
miniaturization Miniaturization ( Br.Eng.: ''Miniaturisation'') is the trend to manufacture ever smaller mechanical, optical and electronic products and devices. Examples include miniaturization of mobile phones A mobile phone, cellular phone, cell phone, ...
, and can be easily scaled down to smaller dimensions. They consume significantly less power, and allow much higher density, than bipolar transistors. MOSFETs can be much smaller than BJTs, about one-twentieth of the size by the early 1990s. MOSFETs also have faster switching speed, with rapid on–off
electronic switch In electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow by amplifier, amplifica ...
ing that makes them ideal for generating
pulse train In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their ...
s, the basis for digital signals. in contrast to BJTs which more slowly generate analog signals resembling
sine waves A sine wave or sinusoid is a mathematical curve that describes a smooth periodic oscillation Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or ...
. MOSFETs are also cheaper and have relatively simple processing steps, resulting in high manufacturing yield. MOSFETs thus enable
large-scale integration An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit i ...
(LSI), and are ideal for
digital circuits Digital electronics is a field of electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control elect ...
, as well as
linear Linearity is the property of a mathematical relationship (''function Function or functionality may refer to: Computing * Function key A function key is a key on a computer A computer is a machine that can be programmed to carry out se ...
analog circuits Analogue electronics ( en-US, analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relations ...
. The MOSFET has been variously described as the most important
transistor upright=1.4, gate Candi bentar, a typical Indonesian gate that is often found on the islands of Java">Indonesia.html" ;"title="Candi bentar, a typical Indonesia">Candi bentar, a typical Indonesian gate that is often found on the islands o ...

transistor
, the most important device in the electronics industry, arguably the most important device in the computing industry, one of the most important developments in
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
technology, and possibly the most important invention in electronics. The MOSFET has been the fundamental building block of modern
digital electronics Digital electronics is a field of electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physica ...
, during the
digital revolution The Digital Revolution (also known as the Third Industrial Revolution) is the shift from mechanical and analogue electronic technology Technology ("science of craft", from Ancient Greek, Greek , ''techne'', "art, skill, cunning of hand"; ...
,
information revolution The term information revolution describes current economic, social and technological trends beyond the Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Europe and the United States, in the p ...
,
information age#REDIRECT Information Age The Information Age (also known as the Computer Age, Digital Age, or New Media Age) is a historical periodHuman history is commonly divided into three main Era, eras — Ancient history, Ancient, Post-classical history, ...
, and
silicon age Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...
. MOSFETs have been the driving force behind the computer revolution, and the technologies enabled by it. The rapid progress of the electronics industry during the late 20th to early 21st centuries was achieved by rapid
MOSFET scaling The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor The field-effect trans ...
(
Dennard scalingDennard may refer to: People with the surname * Alfonzo Dennard, a professional American football cornerback, cousin to Darqueze * Amery Dennard, known as Big Herk, an American rapper * Brazeal Dennard, an American singer and educator * Darqueze ...
and
Moore's law Moore's law is the observation that Transistor count, the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and Forecasting, projection of a historical trend. Rather than a ph ...
), down to the level of
nanoelectronic Nanoelectronics refers to the use of nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and Supramolecular complex, supramolecular scale for industrial purposes. The earliest, widespread de ...
s in the early 21st century. The MOSFET revolutionized the world during the information age, with its high density enabling a
computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Computer program, programs. These ...

computer
to exist on a few small IC chips rather than filling a room, and later making possible digital
communications technology Information and communications technology (ICT) is an extensional term for information technology (IT) that stresses the role of unified communications and the integration of telecommunications Telecommunication is the transmission of informa ...
such as
smartphones A smartphone is a portable device A mobile device (or handheld computer) is a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can per ...

smartphones
. The MOSFET is the most widely manufactured device in history. The MOSFET generates annual sales of as of 2015. Between 1960 and 2018, an estimated total of 13
sextillion This article lists and discusses the usage and derivation of names of large numbers, together with their possible extensions. The following table lists those names of large number Numbers that are significantly larger than those typically used ...
MOS transistors have been manufactured, accounting for at least 99.9% of all transistors. Digital integrated circuits such as
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip ...

microprocessor
s and memory devices contain thousands to billions of integrated MOSFETs on each device, providing the basic switching functions required to implement
logic gate A logic gate is an idealized model of computation A model is an informative representation of an object, person or system. The term originally denoted the plan A plan is typically any diagram or list of steps with details of timing and resourc ...
s and data storage. There are also memory devices which contain at least a trillion MOS transistors, such as a 256
microSD Secure Digital, officially abbreviated as SD, is a proprietary format, proprietary non-volatile memory, non-volatile memory card format developed by the SD Association, SD Association (SDA) for use in portable devices. The standard was introduc ...
memory card A memory card is an electronic data storage device On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data storage medium. Data Data (; ) are individual facts, statistics ...

memory card
, larger than the number of
stars A star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. ...

stars
in the
Milky Way The Milky Way is the galaxy A galaxy is a gravitation Gravity (), or gravitation, is a natural phenomenon by which all things with mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and con ...

Milky Way
galaxy A galaxy is a gravitation Gravity (), or gravitation, is a natural phenomenon by which all things with mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or ...

galaxy
. As of 2010, the operating principles of modern MOSFETs have remained largely the same as the original MOSFET first demonstrated by
Mohamed Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physical chemist Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which ...
and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
in 1960. The
US Patent and Trademark Office The United States Patent and Trademark Office (USPTO) is an agency in the U.S. Department of Commerce that issues patent NPOV disputes from March 2021 A patent is a Title (property), title that gives its owner the legal right to exclude o ...
calls the MOSFET a "groundbreaking invention that transformed life and culture around the world" and the
Computer History Museum The Computer History Museum (CHM) is a museum of computer history, located in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the information age, and explores the computing revolution and its impact on s ...
credits it with "irrevocably changing the human experience." The MOSFET was also the basis for
Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel Alfred Bernhard Nobel ( , ; 21 October 1833 – 10 December 1896) was a Swedish chemist, engineer, inventor, busines ...
winning breakthroughs such as the
quantum Hall effect The quantum Hall effect (or integer quantum Hall effect) is a quantized version of the Hall effect The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric ...

quantum Hall effect
and the
charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD), though there was never any Nobel Prize given for the MOSFET itself. In a 2018 note on
Jack Kilby Jack St. Clair Kilby (November 8, 1923 – June 20, 2005) was an American electrical engineer who took part (along with Robert Noyce of Fairchild) in the realization of the first integrated circuit while working at Texas Instruments (TI) in 1 ...
's
Nobel Prize for Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
for his part in the invention of the integrated circuit, the
Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences ( Swedish: ''Kungliga Vetenskapsakademien'') is one of the royal academies of Sweden Sweden ( sv, Sverige ), officially the Kingdom of Sweden ( sv, links=no, Konungariket Sverige ), is a Nordic co ...
specifically mentioned the MOSFET and the microprocessor as other important inventions in the evolution of
microelectronics Microelectronics is a subfield of electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physica ...
. The MOSFET is also included on the
list of IEEE milestones The following timeline tables list the discoveries and inventions in the history of electrical Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves ...
in electronics, and its inventors Mohamed Atalla and Dawon Kahng entered the
National Inventors Hall of Fame The National Inventors Hall of Fame (NIHF) is an American not-for-profit organization A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and ope ...
in 2009.


Composition

upright=1.2, Photomicrograph of two metal-gate MOSFETs in a test pattern. Probe pads for two gates and three source/drain nodes are labeled. Usually the
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
of choice is
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
. Recently, some chip manufacturers, most notably
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
and
Intel Intel Corporation is an American multinational corporation A multinational company (MNC) is a corporate A corporation is an organization—usually a group of people or a company A company, abbreviated as co., is a Legal personalit ...

Intel
, have started using a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemical bonds. A homonuclear molecule, m ...
of silicon and germanium (
SiGeSiGe ( or ), or silicon-germanium, is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, ...
) in MOSFET channels. Unfortunately, many semiconductors with better electrical properties than silicon, such as
gallium arsenide Gallium Gallium is a chemical element with the Symbol (chemistry), symbol Ga and atomic number 31. Discovered by France, French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in boron group, group 13 of the periodic ta ...

gallium arsenide
, do not form good semiconductor-to-insulator interfaces, and thus are not suitable for MOSFETs. Research continues on creating insulators with acceptable electrical characteristics on other semiconductor materials. To overcome the increase in power consumption due to gate current leakage, a high-κ dielectric is used instead of silicon dioxide for the gate insulator, while polysilicon is replaced by metal gates (e.g.
Intel Intel Corporation is an American multinational corporation A multinational company (MNC) is a corporate A corporation is an organization—usually a group of people or a company A company, abbreviated as co., is a Legal personalit ...

Intel
, 2009). The gate is separated from the channel by a thin insulating layer, traditionally of silicon dioxide and later of
silicon oxynitride Silicon oxynitride is a ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide of rutile. T ...
. Some companies have started to introduce a high-κ dielectric and metal gate combination in the
45 nanometer Per the International Technology Roadmap for Semiconductors The International Technology Roadmap for Semiconductors (ITRS) is a set of documents produced by a group of semiconductor industry The semiconductor industry is the aggregate of co ...
node. When a voltage is applied between the gate and body terminals, the electric field generated penetrates through the oxide and creates an '' inversion layer'' or ''channel'' at the semiconductor-insulator interface due to which makes that part to be less p type and paving the way for conduction of current resulting increase in voltage between gate and body which pushes off the holes and creates layer of immobile carriers which are charged negatively. The inversion layer provides a channel through which current can pass between source and drain terminals. Varying the voltage between the gate and body modulates the conductivity of this layer and thereby controls the current flow between drain and source. This is known as enhancement mode.


Operation

upright=1.2, Metal–oxide–semiconductor structure on p-type silicon


Metal–oxide–semiconductor structure

The traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of
silicon dioxide Silicon dioxide, also known as silica, is an oxide of rutile. Ti(IV) centers are grey; oxygen centers are red. Notice that oxygen forms three bonds to titanium and titanium forms six bonds to oxygen. An oxide () is a chemical compound that con ...
() on top of a
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
substrate, commonly by
thermal oxidation 250px, Furnaces used for diffusion and thermal oxidation at LAAS technological facility in Toulouse, France. In microfabrication Microfabrication is the process of manufacturing, fabricating miniature structures of micrometre scales and smaller. H ...
and depositing a layer of metal or
polycrystalline silicon Polycrystalline silicon, or multicrystalline silicon, also called polysilicon or poly-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry. Polysilicon is produced from Si ...

polycrystalline silicon
(the latter is commonly used). As the silicon dioxide is a
dielectric In electromagnetism Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force i ...

dielectric
material, its structure is equivalent to a planar
capacitor A capacitor is a device that stores electric charge in an electric field. It is a passivity (engineering), passive electronic component with two terminal (electronics), terminals. The effect of a capacitor is known as capacitance. While som ...

capacitor
, with one of the electrodes replaced by a
semiconductor A semiconductor material has an value falling between that of a , such as metallic copper, and an , such as glass. Its falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways ...
. When a voltage is applied across a MOS structure, it modifies the distribution of charges in the semiconductor. If we consider a p-type semiconductor (with N_\text the density of acceptors, ''p'' the density of holes; ''p = N''A in neutral bulk), a positive voltage, V_\text, from gate to body (see figure) creates a depletion layer by forcing the positively charged holes away from the gate-insulator/semiconductor interface, leaving exposed a carrier-free region of immobile, negatively charged acceptor ions (see
doping (semiconductor) In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic sem ...
). If V_\text is high enough, a high concentration of negative charge carriers forms in an '' inversion layer'' located in a thin layer next to the interface between the semiconductor and the insulator. Conventionally, the gate voltage at which the volume density of electrons in the inversion layer is the same as the volume density of holes in the body is called the
threshold voltage The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals. It is an important scaling f ...
. When the voltage between transistor gate and source (''V''GS) exceeds the threshold voltage (''V''th), the difference is known as overdrive voltage. This structure with p-type body is the basis of the n-type MOSFET, which requires the addition of n-type source and drain regions.


MOS capacitors and band diagrams

The MOS capacitor structure is the heart of the MOSFET. Consider a MOS capacitor where the silicon base is of p-type. If a positive voltage is applied at the gate, holes which are at the surface of the p-type substrate will be repelled by the electric field generated by the voltage applied. At first, the holes will simply be repelled and what will remain on the surface will be immobile (negative) atoms of the acceptor type, which creates a depletion region on the surface. Remember that a hole is created by an acceptor atom, e.g. Boron, which has one less electron than Silicon. One might ask how can holes be repelled if they are actually non-entities? The answer is that what really happens is not that a hole is repelled, but electrons are attracted by the positive field, and fill these holes, creating a depletion region where no charge carriers exist because the electron is now fixed onto the atom and immobile. As the voltage at the gate increases, there will be a point at which the surface above the depletion region will be converted from p-type into n-type, as electrons from the bulk area will start to get attracted by the larger electric field. This is known as ''inversion''. The threshold voltage at which this conversion happens is one of the most important parameters in a MOSFET. In the case of a p-type bulk, inversion happens when the intrinsic energy level at the surface becomes smaller than the
Fermi level The Fermi level of a solid-state body is the thermodynamic work required to add one electron to the body. It is a thermodynamic Thermodynamics is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (e ...
at the surface. One can see this from a band diagram. Remember that the Fermi level defines the type of semiconductor in discussion. If the Fermi level is equal to the Intrinsic level, the semiconductor is of intrinsic, or pure type. If the Fermi level lies closer to the conduction band (valence band) then the semiconductor type will be of n-type (p-type). Therefore, when the gate voltage is increased in a positive sense (for the given example), this will "bend" the intrinsic energy level band so that it will curve downwards towards the valence band. If the Fermi level lies closer to the valence band (for p-type), there will be a point when the Intrinsic level will start to cross the Fermi level and when the voltage reaches the threshold voltage, the intrinsic level does cross the Fermi level, and that is what is known as inversion. At that point, the surface of the semiconductor is inverted from p-type into n-type. Remember that as said above, if the Fermi level lies above the Intrinsic level, the semiconductor is of n-type, therefore at Inversion, when the Intrinsic level reaches and crosses the Fermi level (which lies closer to the valence band), the semiconductor type changes at the surface as dictated by the relative positions of the Fermi and Intrinsic energy levels.


Structure and channel formation

upright=1.5, ''Channel formation in nMOS MOSFET shown as band diagram'': Top panels: An applied gate voltage bends bands, depleting holes from surface (left). The charge inducing the bending is balanced by a layer of negative acceptor-ion charge (right). Bottom panel: A larger applied voltage further depletes holes but conduction band lowers enough in energy to populate a conducting channel file:Illustration of C-V measurement.gif, upright=1.5, C–V profile for a bulk MOSFET with different oxide thickness. The leftmost part of the curve corresponds to accumulation. The valley in the middle corresponds to depletion. The curve on the right corresponds to inversion A MOSFET is based on the modulation of charge concentration by a MOS capacitance between a ''body'' electrode and a ''gate'' electrode located above the body and insulated from all other device regions by a gate dielectric layer. If dielectrics other than an oxide are employed, the device may be referred to as a metal-insulator-semiconductor FET (MISFET). Compared to the MOS capacitor, the MOSFET includes two additional terminals (''source'' and ''drain''), each connected to individual highly doped regions that are separated by the body region. These regions can be either p or n type, but they must both be of the same type, and of opposite type to the body region. The source and drain (unlike the body) are highly doped as signified by a "+" sign after the type of doping. If the MOSFET is an n-channel or nMOS FET, then the source and drain are ''n+'' regions and the body is a ''p'' region. If the MOSFET is a p-channel or pMOS FET, then the source and drain are ''p+'' regions and the body is a ''n'' region. The source is so named because it is the source of the charge carriers (electrons for n-channel, holes for p-channel) that flow through the channel; similarly, the drain is where the charge carriers leave the channel. The occupancy of the energy bands in a semiconductor is set by the position of the
Fermi level The Fermi level of a solid-state body is the thermodynamic work required to add one electron to the body. It is a thermodynamic Thermodynamics is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (e ...
relative to the semiconductor energy-band edges. With sufficient gate voltage, the valence band edge is driven far from the Fermi level, and holes from the body are driven away from the gate. At larger gate bias still, near the semiconductor surface the conduction band edge is brought close to the Fermi level, populating the surface with electrons in an ''inversion layer'' or ''n-channel'' at the interface between the p region and the oxide. This conducting channel extends between the source and the drain, and current is conducted through it when a voltage is applied between the two electrodes. Increasing the voltage on the gate leads to a higher electron density in the inversion layer and therefore increases the current flow between the source and drain. For gate voltages below the threshold value, the channel is lightly populated, and only a very small subthreshold conduction, subthreshold leakage current can flow between the source and the drain. When a negative gate–source voltage is applied, it creates a ''p-channel'' at the surface of the n region, analogous to the n-channel case, but with opposite polarities of charges and voltages. When a voltage less negative than the threshold value (a negative voltage for the p-channel) is applied between gate and source, the channel disappears and only a very small subthreshold current can flow between the source and the drain. The device may comprise a silicon on insulator device in which a buried oxide is formed below a thin semiconductor layer. If the channel region between the gate dielectric and the buried oxide region is very thin, the channel is referred to as an ultrathin channel region with the source and drain regions formed on either side in or above the thin semiconductor layer. Other semiconductor materials may be employed. When the source and drain regions are formed above the channel in whole or in part, they are referred to as raised source/drain regions.


Modes of operation

file:MOSFET functioning.svg, upright=2, Source tied to the body to ensure no body bias: subthreshold (top left), ohmic mode (top right), active mode at onset of pinch-off (bottom left), and active mode well into pinch-off (bottom right). Channel length modulation is evident. file:mosfet n-ch circuit.svg, upright=1.2, Example application of an n-channel MOSFET. When the switch is pushed, the LED lights up. 090507 brunningsoftware.co.uk The operation of a MOSFET can be separated into three different modes, depending on the voltages at the terminals. In the following discussion, a simplified algebraic model is used. Modern MOSFET characteristics are more complex than the algebraic model presented here.For example, see . The most recent version of the BSIM model is described in For an ''enhancement-mode, n-channel MOSFET'', the three operational modes are: ; Cutoff, subthreshold, and weak-inversion mode (n-channel MOSFET) When ''V''GS < ''V''th: where V_\text is gate-to-source bias and V_\text is the
threshold voltage The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals. It is an important scaling f ...
of the device. According to the basic threshold model, the transistor is turned off, and there is no conduction between drain and source. A more accurate model considers the effect of thermal energy on the Fermi–Dirac distribution of electron energies which allow some of the more energetic electrons at the source to enter the channel and flow to the drain. This results in a subthreshold current that is an exponential function of gate–source voltage. While the current between drain and source should ideally be zero when the transistor is being used as a turned-off switch, there is a weak-inversion current, sometimes called subthreshold leakage. In weak inversion where the source is tied to bulk, the current varies exponentially with V_\text as given approximately by: : I_\text \approx I_\text e^\frac, where I_\text = current at V_\text = V_\text, the thermal voltage V_\text = kT/q and the slope factor ''n'' is given by: : n = 1 + \frac, \, with C_\text = capacitance of the depletion layer and C_\text = capacitance of the oxide layer. This equation is generally used, but is only an adequate approximation for the source tied to the bulk. For the source not tied to the bulk, the subthreshold equation for drain current in saturation is : I_\text \approx I_\text e^\frac, where the \kappa is the channel divider that is given by: : \kappa = \frac, with C_\text = capacitance of the depletion layer and C_\text = capacitance of the oxide layer. In a long-channel device, there is no drain voltage dependence of the current once V_\text \gg V_\text, but as channel length is reduced drain-induced barrier lowering introduces drain voltage dependence that depends in a complex way upon the device geometry (for example, the channel doping, the junction doping and so on). Frequently, threshold voltage ''V''th for this mode is defined as the gate voltage at which a selected value of current ''I''D0 occurs, for example, ''I''D0 = 1μA, which may not be the same ''V''th-value used in the equations for the following modes. Some micropower analog circuits are designed to take advantage of subthreshold conduction. By working in the weak-inversion region, the MOSFETs in these circuits deliver the highest possible transconductance-to-current ratio, namely: g_m/I_\text = 1/\left(nV_\text\right), almost that of a bipolar transistor. The subthreshold ''I–V curve'' depends exponentially upon threshold voltage, introducing a strong dependence on any manufacturing variation that affects threshold voltage; for example: variations in oxide thickness, junction depth, or body doping that change the degree of drain-induced barrier lowering. The resulting sensitivity to fabricational variations complicates optimization for leakage and performance. file:IvsV mosfet.svg, upright=1.2, MOSFET drain current vs. drain-to-source voltage for several values of V_\text - V_\text; the boundary between ''linear'' (''Ohmic'') and ''saturation'' (''active'') modes is indicated by the upward curving parabola file:Mosfet linear.svg, upright=1.2, Cross section of a MOSFET operating in the linear (Ohmic) region; strong inversion region present even near drain file:Mosfet saturation.svg, upright=1.2, Cross section of a MOSFET operating in the saturation (active) region; channel exhibits channel length modulation, channel pinching near drain ; Triode mode or linear region, also known as the ohmic mode (n-channel MOSFET) When ''V''GS > ''V''th and ''V''DS < ''V''GS − ''V''th: The transistor is turned on, and a channel has been created which allows current between the drain and the source. The MOSFET operates like a resistor, controlled by the gate voltage relative to both the source and drain voltages. The current from drain to source is modeled as: :I_\text = \mu_n C_\text\frac \left[ \left(V_\text - V_\right)V_\text - \frac \right] (1 + \lambda V_) where \mu_n is the charge-carrier effective mobility, W is the gate width, L is the gate length and C_\text is the gate oxide capacitance per unit area. The transition from the exponential subthreshold region to the triode region is not as sharp as the equations suggest. ; Saturation or active mode (n-channel MOSFET) When ''VGS > V''th and ''VDS'' ≥ (V''GS – V''th): The switch is turned on, and a channel has been created, which allows current between the drain and source. Since the drain voltage is higher than the source voltage, the electrons spread out, and conduction is not through a narrow channel but through a broader, two- or three-dimensional current distribution extending away from the interface and deeper in the substrate. The onset of this region is also known as channel length modulation, pinch-off to indicate the lack of channel region near the drain. Although the channel does not extend the full length of the device, the electric field between the drain and the channel is very high, and conduction continues. The drain current is now weakly dependent upon drain voltage and controlled primarily by the gate–source voltage, and modeled approximately as: : I_\text = \frac\frac\left[V_\text - V_\text\right]^2 \left[1 + \lambda (V_\text - V_\text)\right]. The additional factor involving λ, the channel-length modulation parameter, models current dependence on drain voltage due to the channel length modulation, effectively similar to the Early effect seen in bipolar devices. According to this equation, a key design parameter, the MOSFET transconductance is: : g_m = \frac = \frac = \frac , where the combination ''V''ov = ''V''GS − ''V''th is called the overdrive voltage, and where ''V''DSsat = ''V''GS − ''V''th accounts for a small discontinuity in I_\text which would otherwise appear at the transition between the triode and saturation regions. Another key design parameter is the MOSFET output resistance r_ = \frac given by: :r_\text \approx \frac. ''r''out is the inverse of ''g''DS where g_\text = \frac. ''I''D is the expression in saturation region. If λ is taken as zero, the resulting infinite output resistance can simplify circuit analysis, however this may lead to unrealistic circuit predictions, particularly in analog circuits. As the channel length becomes very short, these equations become quite inaccurate. New physical effects arise. For example, carrier transport in the active mode may become limited by velocity saturation. When velocity saturation dominates, the saturation drain current is more nearly linear than quadratic in ''V''GS. At even shorter lengths, carriers transport with near zero scattering, known as quasi-ballistic transport. In the ballistic regime, the carriers travel at an injection velocity that may exceed the saturation velocity and approaches the Fermi velocity at high inversion charge density. In addition, drain-induced barrier lowering increases off-state (cutoff) current and requires an increase in threshold voltage to compensate, which in turn reduces the saturation current.


Body effect

file:Inversion with source-body bias.png, upright=1.2, Band diagram showing body effect. ''V''SB splits Fermi levels Fn for electrons and Fp for holes, requiring larger ''V''GB to populate the conduction band in an nMOS MOSFET The occupancy of the energy bands in a semiconductor is set by the position of the Fermi level#"Fermi level" in semiconductor physics, Fermi level relative to the semiconductor energy-band edges. Application of a source-to-substrate reverse bias of the source-body pn-junction introduces a split between the Fermi levels for electrons and holes, moving the Fermi level for the channel further from the band edge, lowering the occupancy of the channel. The effect is to increase the gate voltage necessary to establish the channel, as seen in the figure. This change in channel strength by application of reverse bias is called the 'body effect'. Simply put, using an nMOS example, the gate-to-body bias ''V''GB positions the conduction-band energy levels, while the source-to-body bias VSB positions the electron Fermi level near the interface, deciding occupancy of these levels near the interface, and hence the strength of the inversion layer or channel. The body effect upon the channel can be described using a modification of the threshold voltage, approximated by the following equation: : V_\text = V_ + \gamma \left( \sqrt - \sqrt \right), VTB=VT0 if VSB=0 i.e. threshold voltage for gate and body terminals getting shorted. where ''V''TB is the threshold voltage with substrate bias present, and ''V''T0 is the zero-''V''SB value of threshold voltage, \gamma is the body effect parameter, and 2''φ''B is the approximate potential drop between surface and bulk across the depletion layer when and gate bias is sufficient to ensure that a channel is present. For a uniformly doped p-type substrate with bulk acceptor doping of ''NA'' per unit volume, :\varphi_B = \frac \ln \left(\frac\right) \ , with ''ni'' the intrinsic mobile carrier density per unit volume in the bulk. See, for example, As this equation shows, a reverse bias causes an increase in threshold voltage ''V''TB and therefore demands a larger gate voltage before the channel populates. The body can be operated as a second gate, and is sometimes referred to as the "back gate"; the body effect is sometimes called the "back-gate effect".


Circuit symbols

A variety of symbols are used for the MOSFET. The basic design is generally a line for the channel with the source and drain leaving it at right angles and then bending back at right angles into the same direction as the channel. Sometimes three line segments are used for Channel (transistor), enhancement mode and a solid line for depletion mode (see depletion and enhancement modes). Another line is drawn parallel to the channel for the gate. The ''bulk'' or ''body'' connection, if shown, is shown connected to the back of the channel with an arrow indicating pMOS or nMOS. Arrows always point from P to N, so an NMOS (N-channel in P-well or P-substrate) has the arrow pointing in (from the bulk to the channel). If the bulk is connected to the source (as is generally the case with discrete devices) it is sometimes angled to meet up with the source leaving the transistor. If the bulk is not shown (as is often the case in IC design as they are generally common bulk) an inversion symbol is sometimes used to indicate PMOS, alternatively an arrow on the source may be used in the same way as for bipolar transistors (out for nMOS, in for pMOS). A comparison of enhancement-mode and depletion-mode MOSFET symbols, along with JFET symbols, is available in the table in this section. The orientation of the symbols, most significantly the position of source relative to drain, is such that more positive voltages appear higher on the schematic page than less positive voltages, implying current flowing "down" the page. In schematics where G, S and D are not labeled, the detailed features of the symbol indicate which terminal is source and which is drain. For enhancement-mode and depletion-mode MOSFET symbols (in columns two and five), the source terminal is the one connected to the arrowhead. Additionally, in this diagram, the gate is shown as an "L" shape, whose input leg is closer to S than D, also indicating which is which. However, these symbols are often drawn with a "T" shaped gate (as elsewhere on this page), so it is the arrowhead which must be relied upon to indicate the source terminal. For the symbols in which the bulk, or body, terminal is shown, it is here shown internally connected to the source (i.e., the black arrowhead in the diagrams in columns 2 and 5). This is a typical configuration, but by no means the only important configuration. In general, the MOSFET is a four-terminal device, and in integrated circuits many of the MOSFETs share a body connection, not necessarily connected to the source terminals of all the transistors.


Types of MOSFET


PMOS and NMOS logic

PMOS logic, P-channel MOS (PMOS) logic uses p-channel MOSFETs to implement
logic gate A logic gate is an idealized model of computation A model is an informative representation of an object, person or system. The term originally denoted the plan A plan is typically any diagram or list of steps with details of timing and resourc ...
s and other digital circuits. NMOS logic, N-channel MOS (NMOS) logic uses n-channel MOSFETs to implement logic gates and other digital circuits. For devices of equal current driving capability, n-channel MOSFETs can be made smaller than p-channel MOSFETs, due to p-channel charge carriers (electron hole, holes) having lower electron mobility, mobility than do n-channel charge carriers (electrons), and producing only one type of MOSFET on a silicon substrate is cheaper and technically simpler. These were the driving principles in the design of
NMOS logic N-type metal-oxide-semiconductor logic uses n-type (-) MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of ...
which uses n-channel MOSFETs exclusively. However, unlike CMOS logic (neglecting leakage current), NMOS logic consumes power even when no switching is taking place.
Mohamed Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physical chemist Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which ...
and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
originally demonstrated both pMOS and nMOS devices with 20 µm process, 20 µm and then 10 µm process, 10 µm gate lengths in 1960. Their original MOSFET devices also had a gate oxide thickness of 100 nm. However, the nMOS devices were impractical, and only the pMOS type were practical working devices. A more practical NMOS process was developed several years later. NMOS was initially faster than
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
, thus NMOS was more widely used for computers in the 1970s. With advances in technology, CMOS logic displaced NMOS logic in the mid-1980s to become the preferred process for digital chips.


Complementary MOS (CMOS)

The MOSFET is used in digital complementary metal–oxide–semiconductor (
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
) logic, which uses p- and n-channel MOSFETs as building blocks. Overheating is a major concern in
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
s since ever more transistors are packed into ever smaller chips. CMOS logic reduces power consumption because no current flows (ideally), and thus no Power (physics), power is consumed, except when the inputs to
logic gate A logic gate is an idealized model of computation A model is an informative representation of an object, person or system. The term originally denoted the plan A plan is typically any diagram or list of steps with details of timing and resourc ...
s are being switched. CMOS accomplishes this current reduction by complementing every nMOSFET with a pMOSFET and connecting both gates and both drains together. A high voltage on the gates will cause the nMOSFET to conduct and the pMOSFET not to conduct and a low voltage on the gates causes the reverse. During the switching time as the voltage goes from one state to another, both MOSFETs will conduct briefly. This arrangement greatly reduces power consumption and heat generation. CMOS was developed by
Chih-Tang Sah Chih-Tang "Tom" Sah (; born in November 1932 in Beijing Beijing ( ), Chinese postal romanization, alternatively romanized as Peking ( ), is the Capital city, capital of the People's Republic of China. It is the world's List of national ca ...
and
Frank WanlassDr. Frank Marion Wanlass (May 17, 1933 in Thatcher, AZ – September 9, 2010 in Santa Clara, California California is a U.S. state, state in the Western United States. With over 39.3million residents across a total area of approximately ...
at
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental pr ...
in 1963. CMOS had lower power consumption, but was initially slower than NMOS, which was more widely used for computers in the 1970s. In 1978, Hitachi introduced the twin-well CMOS process, which allowed CMOS to match the performance of NMOS with less power consumption. The twin-well CMOS process eventually overtook NMOS as the most common semiconductor manufacturing process for computers in the 1980s. By the 1970s1980s, CMOS logic consumed over times less power than NMOS logic, and about 100,000 times less power than bipolar transistor-transistor logic (TTL).


Depletion-mode

There are ''depletion-mode'' MOSFET devices, which are less commonly used than the standard ''enhancement-mode'' devices already described. These are MOSFET devices that are doped so that a channel exists even with zero voltage from gate to source. To control the channel, a negative voltage is applied to the gate (for an n-channel device), depleting the channel, which reduces the current flow through the device. In essence, the depletion-mode device is equivalent to a normally closed (on) switch, while the enhancement-mode device is equivalent to a normally open (off) switch. Due to their low noise figure in the radio frequency, RF region, and better gain (electronics)#Power gain, gain, these devices are often preferred to bipolar junction transistors, bipolars in RF front end, RF front-ends such as in television, TV sets. Depletion-mode MOSFET families include BF960 by Siemens and Telefunken, and the BF980 in the 1980s by Philips (later to become NXP Semiconductors), whose derivatives are still used in automatic gain control, AGC and RF frequency mixer, mixer front-ends.


Metal–insulator–semiconductor field-effect transistor (MISFET)

Metal–insulator–semiconductor field-effect-transistor, or ''MISFET'', is a more general term than ''MOSFET'' and a synonym to ''insulated-gate field-effect transistor'' (IGFET). All MOSFETs are MISFETs, but not all MISFETs are MOSFETs. The gate dielectric insulator in a MISFET is
silicon dioxide Silicon dioxide, also known as silica, is an oxide of rutile. Ti(IV) centers are grey; oxygen centers are red. Notice that oxygen forms three bonds to titanium and titanium forms six bonds to oxygen. An oxide () is a chemical compound that con ...
in a MOSFET, but other materials can also be employed. The gate dielectric lies directly below the gate electrode and above the channel (semiconductor), channel of the MISFET. The term ''metal'' is historically used for the gate material, even though now it is usually doping (semiconductor), highly doped
polysilicon Polycrystalline silicon, or multicrystalline silicon, also called polysilicon or poly-Si, is a high purity, polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose const ...
or some other non-metal. Insulator types may be: * Silicon dioxide, in MOSFETs * Organic insulators (e.g., undoped trans-polyacetylene; cyanoethyl pullulan, CEP), for organic-based FETs.


Floating-gate MOSFET (FGMOS)

The floating-gate MOSFET (FGMOS) is a type of MOSFET where the gate is electrically isolated, creating a floating node in DC and a number of secondary gates or inputs are deposited above the floating gate (FG) and are electrically isolated from it. The first report of a floating-gate MOSFET (FGMOS) was made by
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
(co-inventor of the original MOSFET) and Simon Min Sze in 1967. The FGMOS is commonly used as a floating-gate memory cell (computing), memory cell, the digital storage element in EPROM, EEPROM and Flash memory, flash memories. Other uses of the FGMOS include a neuronal computational element in neural networks, analog storage element, digital potentiometers and single-transistor Digital-to-analog converter, DACs.


Power MOSFET

file:D2PAK.JPG, upright=1.2, Two
power MOSFET A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS tr ...
s in D2PAK surface-mount technology, surface-mount packages. Operating as switches, each of these components can sustain a blocking voltage of 120volts, V in the ''off'' state, and can conduct a con­ti­nuous current of 30 amperes, A in the ''on'' state, dissipating up to about 100 watt, W and controlling a load of over 2000 W. A matchstick is pictured for scale. file:Power mos cell layout.svg, upright=1.2, Cross section of a
power MOSFET A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS tr ...
, with square cells. A typical transistor is constituted of several thousand cells Power MOSFETs have a different structure. As with most power devices, the structure is vertical and not planar. Using a vertical structure, it is possible for the transistor to sustain both high blocking voltage and high current. The voltage rating of the transistor is a function of the doping and thickness of the N-epitaxy, epitaxial layer (see cross section), while the current rating is a function of the channel width (the wider the channel, the higher the current). In a planar structure, the current and breakdown voltage ratings are both a function of the channel dimensions (respectively width and length of the channel), resulting in inefficient use of the "silicon estate". With the vertical structure, the component area is roughly proportional to the current it can sustain, and the component thickness (actually the N-epitaxial layer thickness) is proportional to the breakdown voltage. Power MOSFETs with lateral structure are mainly used in high-end audio amplifiers and high-power PA systems. Their advantage is a better behaviour in the saturated region (corresponding to the linear region of a bipolar transistor) than the vertical MOSFETs. Vertical MOSFETs are designed for switching applications. The power MOSFET, which is commonly used in power electronics, was developed in the early 1970s. The power MOSFET enables low gate drive power, fast switching speed, and advanced paralleling capability.


Double-diffused metal–oxide–semiconductor (DMOS)

There are ''Power MOSFET, VDMOS'' (vertical double-diffused metal oxide semiconductor) and ''LDMOS'' (lateral double-diffused metal oxide semiconductor). Most power MOSFETs are made using this technology.


MOS capacitor

The MOS capacitor is part of the MOSFET structure, where the MOS capacitor is flanked by two p–n junctions. The MOS capacitor is widely used as a storage capacitor in
memory chip Semiconductor memory is a digital electronics, digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to MOS memory, where data is stored within metal–oxide–semiconductor (MOS) memo ...
s, and as the basic building block of the
charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) in image sensor technology. In Dynamic random-access memory, DRAM (dynamic random-access memory), each memory cell (computing), memory cell typically consists of a MOSFET and MOS capacitor.


Thin-film transistor (TFT)

The thin-film transistor (TFT) is a type of MOSFET distinct from the standard bulk MOSFET. The first TFT was invented by Paul K. Weimer at
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric General Electric Company (GE) is an American Multination ...
in 1962, building on the earlier work of Atalla and Kahng on MOSFETs. The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of
RCA Laboratories The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric General Electric Company (GE) is an American Multination ...
in 1968. Lechner, F. J. Marlowe, E. O. Nester and J. Tults demonstrated the concept in 1968 with an 18x2 matrix dynamic scattering LCD that used standard discrete MOSFETs, as TFT performance was not adequate at the time.


Bipolar–MOS transistors

BiCMOS is an
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
that combines BJT and
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
transistors on a single chip. The insulated-gate bipolar transistor (IGBT) is a power transistor with characteristics of both a MOSFET and
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
(BJT).


MOS sensors

A number of MOSFET sensors have been developed, for measuring physics, physical, chemistry, chemical, biological and environmental parameters. The earliest MOSFET sensors include the open-gate FET (OGFET) introduced by Johannessen in 1970, the ion-sensitive field-effect transistor (ISFET) invented by Piet Bergveld in 1970, the adsorption FET (ADFET) patented by P.F. Cox in 1974, and a hydrogen-sensitive MOSFET demonstrated by I. Lundstrom, M.S. Shivaraman, C.S. Svenson and L. Lundkvist in 1975. The ISFET is a special type of MOSFET with a gate at a certain distance, and where the
metal gate A metal gate, in the context of a lateral metal–oxide–semiconductor (MOS) stack, is the gate electrode separated by an oxide from the transistor's channel – the gate material is made from a metal. In most MOS transistors since about the mid 1 ...
is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode. By the mid-1980s, numerous other MOSFET sensors had been developed, including the gas sensor FET (GASFET), surface accessible FET (SAFET), charge flow transistor (CFT), pressure sensor FET (PRESSFET), chemical field-effect transistor (ChemFET), ISFET, reference ISFET (REFET), Bio-FET, biosensor FET (BioFET), Bio-FET, enzyme-modified FET (ENFET) and immunologically modified FET (IMFET). By the early 2000s, BioFET types such as the DNA field-effect transistor (DNAFET), Genetically modified, gene-modified FET (GenFET) and Membrane potential, cell-potential BioFET (CPFET) had been developed. The two main types of image sensors used in digital imaging technology are the
charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) and the active-pixel sensor (CMOS sensor). Both CCD and CMOS sensors are based on MOS technology, with the CCD based on MOS capacitors and the CMOS sensor based on MOS transistors.


Multi-gate field-effect transistor (MuGFET)

file:FINFET MOSFET.png, upright=1.2, A FinFET (fin field-effect transistor), a type of multi-gate MOSFET. The dual-gate MOSFET (DGMOS) has a tetrode configuration, where both gates control the current in the device. It is commonly used for small-signal devices in radio frequency applications where biasing the drain-side gate at constant potential reduces the gain loss caused by Miller effect, replacing two separate transistors in cascode configuration. Other common uses in RF circuits include gain control and mixing (frequency conversion). The ''tetrode'' description, though accurate, does not replicate the vacuum-tube tetrode. Vacuum-tube tetrodes, using a screen grid, exhibit much lower grid-plate capacitance and much higher output impedance and voltage gains than triode vacuum tubes. These improvements are commonly an order of magnitude (10 times) or considerably more. Tetrode transistors (whether bipolar junction or field-effect) do not exhibit improvements of such a great degree. The FinFET is a double-gate silicon on insulator, silicon-on-insulator device, one of a number of geometries being introduced to mitigate the effects of short channels and reduce drain-induced barrier lowering. The ''fin'' refers to the narrow channel between source and drain. A thin insulating oxide layer on either side of the fin separates it from the gate. SOI FinFETs with a thick oxide on top of the fin are called ''double-gate'' and those with a thin oxide on top as well as on the sides are called ''triple-gate'' FinFETs. A double-gate MOSFET transistor was first demonstrated in 1984 by Electrotechnical Laboratory researchers Toshihiro Sekigawa and Yutaka Hayashi. A GAAFET (gate-all-around MOSFET), a type of Multigate device, multi-gate non-planar 3D transistor, was first demonstrated in 1988 by a Toshiba research team including Fujio Masuoka, H. Takato and K. Sunouchi. The FinFET (fin field-effect transistor), a type of 3D non-planar double-gate MOSFET, originated from the research of Digh Hisamoto and his team at Hitachi, Hitachi Central Research Laboratory in 1989. The development of nanowire multi-gate MOSFETs have since become fundamental to nanoelectronics.


Quantum field-effect transistor (QFET)

A QFET, quantum field-effect transistor (QFET) or quantum well field-effect transistor (QWFET) is a type of MOSFET that takes advantage of quantum tunneling to greatly increase the speed of transistor operation.


Radiation-hardened-by-design (RHBD)

Semiconductor sub-micrometer and nanometer electronic circuits are the primary concern for operating within the normal tolerance in harsh radiation environments like outer space. One of the design approaches for making a radiation hardening, radiation-hardened-by-design (RHBD) device is enclosed-layout-transistor (ELT). Normally, the gate of the MOSFET surrounds the drain, which is placed in the center of the ELT. The source of the MOSFET surrounds the gate. Another RHBD MOSFET is called H-Gate. Both of these transistors have very low leakage current with respect to radiation. However, they are large in size and take more space on silicon than a standard MOSFET. In older STI (shallow trench isolation) designs, radiation strikes near the silicon oxide region cause the channel inversion at the corners of the standard MOSFET due to accumulation of radiation induced trapped charges. If the charges are large enough, the accumulated charges affect STI surface edges along the channel near the channel interface (gate) of the standard MOSFET. Thus the device channel inversion occurs along the channel edges and the device creates an off-state leakage path, causing the device to turn on. So the reliability of circuits degrades severely. The ELT offers many advantages. These advantages include improvement of reliability (semiconductor), reliability by reducing unwanted surface inversion at the gate edges that occurs in the standard MOSFET. Since the gate edges are enclosed in ELT, there is no gate oxide edge (STI at gate interface), and thus the transistor off-state leakage is reduced considerably. Low-power microelectronic circuits including computers, communication devices and monitoring systems in the space shuttle and satellites are very different to what is used on earth. They require radiation (high-speed atomic particles like proton and neutron, solar flare magnetic energy dissipation in Earth's space, energetic cosmic rays like X-ray, gamma ray etc.) tolerant circuits. These special electronics are designed by applying different techniques using RHBD MOSFETs to ensure safer journeys and space-walks for astronauts.


Applications

The MOSFET generally forms the basis of modern
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic particles are smaller than ...
, as the dominant transistor in
digital circuits Digital electronics is a field of electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control elect ...
as well as analog integrated circuits. It is the basis for numerous modern technologies, and is commonly used for a wide range of applications. According to Jean-Pierre Colinge, numerous modern technologies would not exist without the MOSFET, such as the modern computer industry, digital telecommunication systems, video games, pocket calculators, and digital wristwatches, for example. Discrete MOSFET devices are widely used in applications such as switch mode power supply, switch mode power supplies, variable-frequency drives and other power electronics applications where each device may be switching thousands of watts. Radio-frequency amplifiers up to the UHF spectrum use MOSFET transistors as analog signal and power amplifiers. Radio systems also use MOSFETs as oscillators, or frequency mixer, mixers to convert frequencies. MOSFET devices are also applied in audio-frequency power amplifiers for public address systems, sound reinforcement and home and automobile sound systems. MOSFETs in
integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indivi ...

integrated circuits
are the primary elements of computer processors, semiconductor memory, image sensors, and most other types of integrated circuits.


MOS integrated circuit (MOS IC)

The MOSFET is the most widely used type of transistor and the most critical device component in
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of indiv ...

integrated circuit
(IC) chips. The monolithic integrated circuit chip was enabled by the surface passivation process, which electrically stabilized
silicon Silicon is a chemical element with the Symbol (chemistry), symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a Tetravalence, tetravalent metalloid and semiconductor. It is a member ...

silicon
surfaces via
thermal oxidation 250px, Furnaces used for diffusion and thermal oxidation at LAAS technological facility in Toulouse, France. In microfabrication Microfabrication is the process of manufacturing, fabricating miniature structures of micrometre scales and smaller. H ...
, making it possible to semiconductor device fabrication, fabricate monolithic integrated circuit chips using silicon. The surface passivation process was developed by
Mohamed M. Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physical chemist Physical chemistry is the study of macroscopic The macroscopic scale is the length scale on which ...

Mohamed M. Atalla
at
Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories (1925–1984)) is an American industrial research and scientific development company A company, abbrev ...
in 1957. This was the basis for the planar process, developed by
Jean HoerniJean Amédée Hoerni (September 26, 1924 – January 12, 1997) was a Swiss-American engineer. He was a silicon transistor pioneer, and a member of the " traitorous eight". He developed the planar process, an important technology for reliably fabr ...
at
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental pr ...
in early 1959, which was critical to the invention of the monolithic integrated circuit chip by Robert Noyce later in 1959. The same year, Atalla used his surface passivation process to invent the MOSFET with
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
at Bell Labs. This was followed by the development of clean rooms to reduce contamination to levels never before thought necessary, and coincided with the development of photolithography which, along with surface passivation and the planar process, allowed circuits to be made in few steps. Mohamed Atalla first proposed the concept of the MOS integrated circuit (MOS IC) chip in 1960, noting that the MOSFET's ease of Semiconductor device fabrication, fabrication made it useful for integrated circuits. In contrast to bipolar transistors which required a number of steps for the p–n junction isolation of transistors on a chip, MOSFETs required no such steps but could be easily isolated from each other. Its advantage for integrated circuits was re-iterated by Dawon Kahng in 1961. The Silicon, Si– SiO2 system possessed the technical attractions of low cost of production (on a per circuit basis) and ease of integration. These two factors, along with its #Scaling, rapidly scaling miniaturization and low energy consumption, led to the MOSFET becoming the most widely used type of transistor in IC chips. The earliest experimental MOS IC to be demonstrated was a 16-transistor chip built by Fred Heiman and Steven Hofstein at
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric General Electric Company (GE) is an American Multination ...
in 1962.
General Microelectronics General Microelectronics (GMe) was an American semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic copper ...
later introduced the first commercial MOS integrated circuits in 1964, consisting of 120 p-channel transistors. It was a 20-bit shift register, developed by Robert Norman and
Frank WanlassDr. Frank Marion Wanlass (May 17, 1933 in Thatcher, AZ – September 9, 2010 in Santa Clara, California California is a U.S. state, state in the Western United States. With over 39.3million residents across a total area of approximately ...
. In 1968,
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental pr ...
researchers
Federico Faggin Federico Faggin (, ; born 1 December 1941) is an Italian-American physicist, engineer, inventor and entrepreneur. He is best known for designing the first commercial microprocessor, the Intel 4004. He led the Intel 4004, 4004 (MCS-4) project and ...

Federico Faggin
and Tom Klein developed the first silicon-gate MOS IC.


MOS large-scale integration (MOS LSI)

With its high scalability, and much lower power consumption and higher density than bipolar junction transistors, the MOSFET made it possible to build Large scale integration, high-density IC chips. By 1964, MOS chips had reached higher
transistor density upright=1.4, gate File:Kebun Raya Bali Candi Bentar IMG 8794.jpg, Candi bentar, a typical Indonesian gate that is often found on the islands of Java and Bali A gate or gateway is a point of entry to or from a space enclosed by walls. The w ...
and lower manufacturing costs than bipolar junction transistor, bipolar chips. MOS chips further increased in complexity at a rate predicted by
Moore's law Moore's law is the observation that Transistor count, the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and Forecasting, projection of a historical trend. Rather than a ph ...
, leading to
large-scale integration An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit i ...
(LSI) with hundreds of MOSFETs on a chip by the late 1960s. MOS technology enabled the integration of more than 10,000 transistors on a single LSI chip by the early 1970s, before later enabling very large-scale integration (VLSI).


Microprocessors

The MOSFET is the basis of every
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip ...

microprocessor
, and was responsible for the invention of the microprocessor. The origins of both the microprocessor and the microcontroller can be traced back to the invention and development of MOS technology. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on a single MOS LSI chip. The microprocessor chronology, earliest microprocessors were all MOS chips, built with MOS LSI circuits. The first multi-chip microprocessors, the Four-Phase Systems AL1 in 1969 and the Garrett AiResearch MP944 in 1970, were developed with multiple MOS LSI chips. The first commercial single-chip microprocessor, the Intel 4004, was developed by
Federico Faggin Federico Faggin (, ; born 1 December 1941) is an Italian-American physicist, engineer, inventor and entrepreneur. He is best known for designing the first commercial microprocessor, the Intel 4004. He led the Intel 4004, 4004 (MCS-4) project and ...

Federico Faggin
, using his silicon-gate MOS IC technology, with
Intel Intel Corporation is an American multinational corporation A multinational company (MNC) is a corporate A corporation is an organization—usually a group of people or a company A company, abbreviated as co., is a Legal personalit ...

Intel
engineers Marcian Hoff and Stan Mazor, and Busicom engineer Masatoshi Shima. With the arrival of
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "see-moss"), also known as complementary-symmetry metal–oxide–semiconductor (COS-MOS), is a type of metal–oxide–semiconductor field-effect transistor The metal–oxide–sem ...
microprocessors in 1975, the term "MOS microprocessors" began to refer to chips fabricated entirely from PMOS logic or fabricated entirely from
NMOS logic N-type metal-oxide-semiconductor logic uses n-type (-) MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of ...
, contrasted with "CMOS microprocessors" and "bipolar bit-slice processors".


CMOS circuits


Digital

The growth of digital technologies like the
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip ...

microprocessor
has provided the motivation to advance MOSFET technology faster than any other type of silicon-based transistor. A big advantage of MOSFETs for digital switching is that the oxide layer between the gate and the channel prevents DC current from flowing through the gate, further reducing power consumption and giving a very large input impedance. The insulating oxide between the gate and channel effectively isolates a MOSFET in one logic stage from earlier and later stages, which allows a single MOSFET output to drive a considerable number of MOSFET inputs. Bipolar transistor-based logic (such as transistor-transistor logic, TTL) does not have such a high fanout capacity. This isolation also makes it easier for the designers to ignore to some extent loading effects between logic stages independently. That extent is defined by the operating frequency: as frequencies increase, the input impedance of the MOSFETs decreases.


Analog

The MOSFET's advantages in digital circuits do not translate into supremacy in all analog circuits. The two types of circuit draw upon different features of transistor behavior. Digital circuits switch, spending most of their time either fully on or fully off. The transition from one to the other is only of concern with regards to speed and charge required. Analog circuits depend on operation in the transition region where small changes to ''V'' can modulate the output (drain) current. The JFET and
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
(BJT) are preferred for accurate matching (of adjacent devices in integrated circuits), higher transconductance and certain temperature characteristics which simplify keeping performance predictable as circuit temperature varies. Nevertheless, MOSFETs are widely used in many types of analog circuits because of their own advantages (zero gate current, high and adjustable output impedance and improved robustness vs. BJTs which can be permanently degraded by even lightly breaking down the emitter-base). The characteristics and performance of many analog circuits can be scaled up or down by changing the sizes (length and width) of the MOSFETs used. By comparison, in bipolar transistors the size of the device does not significantly affect its performance. MOSFETs' ideal characteristics regarding gate current (zero) and drain-source offset voltage (zero) also make them nearly ideal switch elements, and also make switched capacitor analog circuits practical. In their linear region, MOSFETs can be used as precision resistors, which can have a much higher controlled resistance than BJTs. In high power circuits, MOSFETs sometimes have the advantage of not suffering from thermal runaway as BJTs do. Also, MOSFETs can be configured to perform as capacitors and gyrator, gyrator circuits which allow op-amps made from them to appear as inductors, thereby allowing all of the normal analog devices on a chip (except for diodes, which can be made smaller than a MOSFET anyway) to be built entirely out of MOSFETs. This means that complete analog circuits can be made on a silicon chip in a much smaller space and with simpler fabrication techniques. MOSFETS are ideally suited to switch inductive loads because of tolerance to inductive kickback. Some ICs combine analog and digital MOSFET circuitry on a single mixed-signal integrated circuit, making the needed board space even smaller. This creates a need to isolate the analog circuits from the digital circuits on a chip level, leading to the use of isolation rings and silicon on insulator (SOI). Since MOSFETs require more space to handle a given amount of power than a BJT, fabrication processes can incorporate BJTs and MOSFETs into a single device. Mixed-transistor devices are called bi-FETs (bipolar FETs) if they contain just one BJT-FET and BiCMOS (bipolar-CMOS) if they contain complementary BJT-FETs. Such devices have the advantages of both insulated gates and higher current density. In the late 1980s, Asad Abidi pioneered RF CMOS technology, which uses MOS VLSI circuits, while working at UCLA. This changed the way in which RF circuits were designed, away from discrete bipolar transistors and towards CMOS integrated circuits. As of 2008, the radio transceivers in all wireless networking devices and modern mobile phones are mass-produced as RF CMOS devices. RF CMOS is also used in nearly all modern Bluetooth and wireless LAN (WLAN) devices.


MOS memory

The advent of the MOSFET enabled the practical use of MOS transistors as memory cell (computing), memory cell storage elements, a function previously served by magnetic-core memory, magnetic cores in computer memory. The first modern computer memory was introduced in 1965, when John Schmidt at
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental pr ...
designed the first MOS semiconductor memory, a 64-bit MOS Static random-access memory, SRAM (static random-access memory). SRAM became an alternative to magnetic-core memory, but required six MOS transistors for each bit of data. MOS technology is the basis for DRAM (dynamic random-access memory). In 1966, Dr. Robert H. Dennard at the
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
Thomas J. Watson Research Center was working on MOS memory. While examining the characteristics of MOS technology, he found it was capable of building capacitors, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell. In 1967, Dennard filed a patent under IBM for a single-transistor DRAM (dynamic random-access memory) memory cell, based on MOS technology. MOS memory enabled higher performance, was cheaper, and consumed less power, than magnetic-core memory, leading to MOS memory overtaking magnetic core memory as the dominant computer memory technology by the early 1970s.
Frank WanlassDr. Frank Marion Wanlass (May 17, 1933 in Thatcher, AZ – September 9, 2010 in Santa Clara, California California is a U.S. state, state in the Western United States. With over 39.3million residents across a total area of approximately ...
, while studying MOSFET structures in 1963, noted the movement of charge through Gate oxide, oxide onto a Metal gate, gate. While he did not pursue it, this idea would later become the basis for EPROM (erasable programmable read-only memory) technology. In 1967,
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics Solid-state electronics means semiconductor A semiconductor material has an el ...

Dawon Kahng
and Simon Min Sze proposed that floating-gate memory cells, consisting of floating-gate MOSFETs (FGMOS), could be used to produce EPROM, reprogrammable ROM (read-only memory). Floating-gate memory cells later became the basis for non-volatile memory (NVM) technologies including EPROM, EEPROM (electrically erasable programmable ROM) and flash memory.


Consumer electronics

MOSFETs are widely used in consumer electronics. One of the earliest influential consumer electronic products enabled by MOS LSI circuits was the electronic pocket calculator, as MOS LSI technology enabled large amounts of computational capability in small packages. In 1965, the Victor Technology, Victor 3900 desktop calculator was the first MOS calculator, with 29 MOS chips. In 1967, the Texas Instruments Cal-Tech was the first prototype electronic handheld calculator, with three MOS LSI chips, and it was later released as the Canon Inc., Canon Pocketronic in 1970. The Sharp QT-8D desktop calculator was the first mass-produced LSI MOS calculator in 1969, and the Sharp EL-8 which used four MOS LSI chips was the first commercial electronic handheld calculator in 1970. The first true electronic pocket calculator was the Busicom LE-120A HANDY LE, which used a single MOS LSI System on a chip, calculator-on-a-chip from Mostek, and was released in 1971. By 1972, MOS LSI circuits were commercialized for numerous other applications. MOSFETs are fundamental to information and communications technology (ICT), including modern computers, modern computing, telecommunications, the communications infrastructure, the Internet, digital telephony, wireless telecommunications, and mobile networks. According to Colinge, the modern computer industry and digital telecommunication systems would not exist without the MOSFET. Advances in MOS technology has been the most important contributing factor in the rapid rise of network bandwidth in telecommunication networks, with bandwidth doubling every 18 months, from bits per second to terabit per second, terabits per second (Edholm's law).


MOS sensors

MOS sensors, also known as MOSFET sensors, are widely used to measure physics, physical, chemistry, chemical, biological and environmental parameters. The ion-sensitive field-effect transistor (ISFET), for example, is widely used in biomedical applications. MOS Chemiresistor, chemiresistors and MOSFETs have also been extensively shown to have promising applications is gas sensing either as single sensor devices or as components in Chemical sensor array, chemical sensor arrays. MOSFETs are also widely used in microelectromechanical systems (MEMS), as silicon MOSFETs could interact and communicate with the surroundings and process things such as chemicals, motions and light. An early example of a MEMS device is the resonant-gate transistor, an adaptation of the MOSFET, developed by Harvey C. Nathanson in 1965. MOS technology is the basis for modern image sensors, including the
charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) and the CMOS active-pixel sensor (CMOS sensor), used in digital imaging and digital cameras. Willard Boyle and George E. Smith developed the CCD in 1969. While researching the MOS process, they realized that an electric charge was the analogy of the magnetic bubble and that it could be stored on a tiny MOS capacitor. As it was fairly straightforward to fabricate a series of MOS capacitors in a row, they connected a suitable voltage to them so that the charge could be stepped along from one to the next. The CCD is a semiconductor circuit that was later used in the first digital video cameras for television broadcasting. The MOS active-pixel sensor (APS) was developed by Tsutomu Nakamura at Olympus Corporation, Olympus in 1985. The CMOS active-pixel sensor was later developed by Eric Fossum and his team at
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agencies of the United States government, independent agency of the Federal government of the United States, U.S. federal government responsible for the civilian Li ...

NASA
's Jet Propulsion Laboratory in the early 1990s.Eric R. Fossum (1993), "Active Pixel Sensors: Are CCD's Dinosaurs?" Proc. SPIE Vol. 1900, pp. 2–14, ''Charge-Coupled Devices and Solid State Optical Sensors III'', Morley M. Blouke; Ed. MOS image sensors are widely used in optical mouse technology. The first optical mouse, invented by Richard F. Lyon at Xerox in 1980, used a 6 µm process, 5µm NMOS logic, NMOS sensor chip. Since the first commercial optical mouse, the IntelliMouse introduced in 1999, most optical mouse devices use CMOS sensors.


Power MOSFETs

The
power MOSFET A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS tr ...
is the most widely used
power device A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics (for example in a switch-mode power supply). Such a device is also called a power device or, when used in an integrated circuit, a power IC. A ...
in the world. Advantages over
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar t ...
s in power electronics include MOSFETs not requiring a continuous flow of drive current to remain in the ON state, offering higher switching speeds, lower switching power losses, lower on-resistances, and reduced susceptibility to thermal runaway. The power MOSFET had an impact on power supplies, enabling higher operating frequencies, size and weight reduction, and increased volume production. Switching power supplies are the most common applications for power MOSFETs. They are also widely used for MOS RF power amplifiers, which enabled the transition of mobile networks from analog to digital in the 1990s. This led to the wide proliferation of wireless mobile networks, which revolutionised telecommunication systems. The LDMOS in particular is the most widely used power amplifier in mobile networks, such as 2G, 3G, 4G, and 5G. Over 50billion discrete power MOSFETs are shipped annually, as of 2018. They are widely used for automotive, Manufacturing, industrial and communications systems in particular. Power MOSFETs are commonly used in automotive electronics, particularly as switching devices in electronic control units, and as power converters in modern electric vehicles. The insulated-gate bipolar transistor (IGBT), a hybrid MOS-bipolar transistor, is also used for a wide variety of applications.


Construction


Gate material

The primary criterion for the gate material is that it is a good conductor (material), conductor. Highly doped
polycrystalline silicon Polycrystalline silicon, or multicrystalline silicon, also called polysilicon or poly-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry. Polysilicon is produced from Si ...

polycrystalline silicon
is an acceptable but certainly not ideal conductor, and also suffers from some more technical deficiencies in its role as the standard gate material. Nevertheless, there are several reasons favoring use of polysilicon: # The
threshold voltage The threshold voltage, commonly abbreviated as Vth, of a field-effect transistor (FET) is the minimum gate-to-source voltage VGS (th) that is needed to create a conducting path between the source and drain terminals. It is an important scaling f ...
(and consequently the drain to source on-current) is modified by the work function difference between the gate material and channel material. Because polysilicon is a semiconductor, its work function can be modulated by adjusting the type and level of doping. Furthermore, because polysilicon has the same bandgap as the underlying silicon channel, it is quite straightforward to tune the work function to achieve low threshold voltages for both NMOS and PMOS devices. By contrast, the work functions of metals are not easily modulated, so tuning the work function to obtain low threshold voltages (LVT) becomes a significant challenge. Additionally, obtaining low-threshold devices on both PMOS and NMOS devices sometimes requires the use of different metals for each device type. While bimetallic integrated circuits (i.e., one type of metal for gate electrodes of NFETS and a second type of metal for gate electrodes of PFETS) are not common, they are known in patent literature and provide some benefit in terms of tuning electrical circuits' overall electrical performance. # The silicon-SiO2 interface has been well studied and is known to have relatively few defects. By contrast many metal-insulator interfaces contain significant levels of defects which can lead to Fermi level pinning, charging, or other phenomena that ultimately degrade device performance. # In the MOSFET fabrication (semiconductor), IC fabrication process, it is preferable to deposit the gate material prior to certain high-temperature steps in order to make better-performing transistors. Such high temperature steps would melt some metals, limiting the types of metal that can be used in a metal-gate-based process. While polysilicon gates have been the de facto standard for the last twenty years, they do have some disadvantages which have led to their likely future replacement by metal gates. These disadvantages include: * Polysilicon is not a great conductor (approximately 1000 times more resistive than metals) which reduces the signal propagation speed through the material. The resistivity can be lowered by increasing the level of doping, but even highly doped polysilicon is not as conductive as most metals. To improve conductivity further, sometimes a high-temperature metal such as tungsten, titanium, cobalt, and more recently nickel is alloyed with the top layers of the polysilicon. Such a blended material is called silicide. The silicide-polysilicon combination has better electrical properties than polysilicon alone and still does not melt in subsequent processing. Also the threshold voltage is not significantly higher than with polysilicon alone, because the silicide material is not near the channel. The process in which silicide is formed on both the gate electrode and the source and drain regions is sometimes called salicide, self-aligned silicide. * When the transistors are extremely scaled down, it is necessary to make the gate dielectric layer very thin, around 1 nm in state-of-the-art technologies. A phenomenon observed here is the so-called Poly Depletion Effect, poly depletion, where a depletion layer is formed in the gate polysilicon layer next to the gate dielectric when the transistor is in the inversion. To avoid this problem, a metal gate is desired. A variety of metal gates such as tantalum, tungsten, tantalum nitride, and titanium nitride are used, usually in conjunction with high-κ dielectrics. An alternative is to use fully silicided polysilicon gates, a process known as FUSI. Present high performance CPUs use metal gate technology, together with high-κ dielectrics, a combination known as ''high-κ, metal gate'' (HKMG). The disadvantages of metal gates are overcome by a few techniques: # The threshold voltage is tuned by including a thin "work function metal" layer between the high-κ dielectric and the main metal. This layer is thin enough that the total work function of the gate is influenced by both the main metal and thin metal work functions (either due to alloying during annealing, or simply due to the incomplete screening by the thin metal). The threshold voltage thus can be tuned by the thickness of the thin metal layer. # High-κ dielectrics are now well studied, and their defects are understood. # HKMG processes exist that do not require the metals to experience high temperature anneals; other processes select metals that can survive the annealing step.


Insulator

As devices are made smaller, insulating layers are made thinner, often through steps of
thermal oxidation 250px, Furnaces used for diffusion and thermal oxidation at LAAS technological facility in Toulouse, France. In microfabrication Microfabrication is the process of manufacturing, fabricating miniature structures of micrometre scales and smaller. H ...
or localised oxidation of silicon (LOCOS). For nano-scaled devices, at some point quantum tunneling, tunneling of carriers through the insulator from the channel to the gate electrode takes place. To reduce the resulting leakage (semiconductors), leakage current, the insulator can be made thinner by choosing a material with a higher dielectric constant. To see how thickness and dielectric constant are related, note that Gauss's law connects field to charge as: : Q = \kappa \epsilon_0 E, with ''Q'' = charge density, κ = dielectric constant, ε0 = permittivity of empty space and ''E'' = electric field. From this law it appears the same charge can be maintained in the channel at a lower field provided κ is increased. The voltage on the gate is given by: : V_\text = V_\text + E\, t_\text = V_\text + \frac, with ''V''G = gate voltage, ''V''ch = voltage at channel side of insulator, and ''t''ins = insulator thickness. This equation shows the gate voltage will not increase when the insulator thickness increases, provided κ increases to keep ''t''ins / κ = constant (see the article on high-κ dielectrics for more detail, and the section in this article on #Increased gate-oxide leakage, gate-oxide leakage). The insulator in a MOSFET is a dielectric which can in any event be silicon oxide, formed by LOCOS but many other dielectric materials are employed. The generic term for the dielectric is gate dielectric since the dielectric lies directly below the gate electrode and above the channel of the MOSFET.


Junction design

The source-to-body and drain-to-body p–n junction, junctions are the object of much attention because of three major factors: their design affects the Current–voltage characteristic, current–voltage (''I–V'') characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and finally, the component of stand-by power dissipation due to junction leakage. The drain induced barrier lowering of the threshold voltage and channel length modulation effects upon ''I-V'' curves are reduced by using shallow junction extensions. In addition, ''halo'' doping can be used, that is, the addition of very thin heavily doped regions of the same doping type as the body tight against the junction walls to limit the extent of depletion regions. The capacitive effects are limited by using raised source and drain geometries that make most of the contact area border thick dielectric instead of silicon. These various features of junction design are shown (with artistic license) in the figure.


Scaling

Over the past decades, the MOSFET (as used for digital logic) has continually been scaled down in size; typical MOSFET channel lengths were once several micrometres, but modern integrated circuits are incorporating MOSFETs with channel lengths of tens of nanometers. Robert H. Dennard, Robert Dennard's work on scaling law, scaling theory was pivotal in recognising that this ongoing reduction was possible. The semiconductor industry maintains a "roadmap", the International Technology Roadmap for Semiconductors, ITRS, which sets the pace for MOSFET development. Historically, the difficulties with decreasing the size of the MOSFET have been associated with the semiconductor device fabrication process, the need to use very low voltages, and with poorer electrical performance necessitating circuit redesign and innovation (small MOSFETs exhibit higher leakage currents and lower output resistance). As of 2019, the smallest MOSFETs in production are 5 nm FinFET semiconductor nodes, manufactured by Samsung Electronics and TSMC. Smaller MOSFETs are desirable for several reasons. The main reason to make transistors smaller is to pack more and more devices in a given chip area. This results in a chip with the same functionality in a smaller area, or chips with more functionality in the same area. Since fabrication costs for a Wafer (electronics), semiconductor wafer are relatively fixed, the cost per integrated circuits is mainly related to the number of chips that can be produced per wafer. Hence, smaller ICs allow more chips per wafer, reducing the price per chip. In fact, over the past 30 years the number of transistors per chip has been doubled every 2–3 years once a new technology node is introduced. For example, the number of MOSFETs in a microprocessor fabricated in a 45 nm technology can well be twice as many as in a 65 nm chip. This doubling of transistor density was first observed by Gordon Moore in 1965 and is commonly referred to as
Moore's law Moore's law is the observation that Transistor count, the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and Forecasting, projection of a historical trend. Rather than a ph ...
. It is also expected that smaller transistors switch faster. For example, one approach to size reduction is a scaling of the MOSFET that requires all device dimensions to reduce proportionally. The main device dimensions are the channel length, channel width, and oxide thickness. When they are scaled down by equal factors, the transistor channel resistance does not change, while gate capacitance is cut by that factor. Hence, the RC delay of the transistor scales with a similar factor. While this has been traditionally the case for the older technologies, for the state-of-the-art MOSFETs reduction of the transistor dimensions does not necessarily translate to higher chip speed because the delay due to interconnections is more significant. Producing MOSFETs with channel lengths much smaller than a micrometre is a challenge, and the difficulties of semiconductor device fabrication are always a limiting factor in advancing integrated circuit technology. Though processes such as atomic layer deposition (atomic layer deposition, ALD) have improved fabrication for small components, the small size of the MOSFET (less than a few tens of nanometers) has created operational problems: ; Higher subthreshold conduction: As MOSFET geometries shrink, the voltage that can be applied to the gate must be reduced to maintain reliability. To maintain performance, the threshold voltage of the MOSFET has to be reduced as well. As threshold voltage is reduced, the transistor cannot be switched from complete turn-off to complete turn-on with the limited voltage swing available; the circuit design is a compromise between strong current in the ''on'' case and low current in the ''off'' case, and the application determines whether to favor one over the other. Subthreshold leakage (including subthreshold conduction, gate-oxide leakage and reverse-biased junction leakage), which was ignored in the past, now can consume upwards of half of the total power consumption of modern high-performance VLSI chips. ; Increased gate-oxide leakage: The gate oxide, which serves as insulator between the gate and channel, should be made as thin as possible to increase the channel conductivity and performance when the transistor is on and to reduce subthreshold leakage when the transistor is off. However, with current gate oxides with a thickness of around 1.2 nanometer, nm (which in silicon is ~5 atoms thick) the quantum mechanics, quantum mechanical phenomenon of Quantum tunneling, electron tunneling occurs between the gate and channel, leading to increased power consumption. Silicon dioxide has traditionally been used as the gate insulator. Silicon dioxide however has a modest dielectric constant. Increasing the dielectric constant of the gate dielectric allows a thicker layer while maintaining a high capacitance (capacitance is proportional to dielectric constant and inversely proportional to dielectric thickness). All else equal, a higher dielectric thickness reduces the quantum tunneling current through the dielectric between the gate and the channel. Insulators that have a larger dielectric constant than silicon dioxide (referred to as high-κ dielectrics), such as group IVb metal silicates e.g. hafnium and zirconium silicates and oxides are being used to reduce the gate leakage from the 45 nanometer technology node onwards. On the other hand, the barrier height of the new gate insulator is an important consideration; the difference in conduction band energy between the semiconductor and the dielectric (and the corresponding difference in valence band energy) also affects leakage current level. For the traditional gate oxide, silicon dioxide, the former barrier is approximately 8 Electronvolt, eV. For many alternative dielectrics the value is significantly lower, tending to increase the tunneling current, somewhat negating the advantage of higher dielectric constant. The maximum gate–source voltage is determined by the strength of the electric field able to be sustained by the gate dielectric before significant leakage occurs. As the insulating dielectric is made thinner, the electric field strength within it goes up for a fixed voltage. This necessitates using lower voltages with the thinner dielectric. ; Increased junction leakage: To make devices smaller, junction design has become more complex, leading to higher Doping (semiconductors), doping levels, shallower junctions, "halo" doping and so forth, all to decrease drain-induced barrier lowering (see the section on #Junction design, junction design). To keep these complex junctions in place, the annealing steps formerly used to remove damage and electrically active defects must be curtailed increasing junction leakage. Heavier doping is also associated with thinner depletion layers and more recombination centers that result in increased leakage current, even without lattice damage. ; Drain-induced barrier lowering (DIBL) and ''V''T roll off: Because of the short-channel effect, channel formation is not entirely done by the gate, but now the drain and source also affect the channel formation. As the channel length decreases, the depletion regions of the source and drain come closer together and make the threshold voltage (''V''T) a function of the length of the channel. This is called ''V''T roll-off. ''V''T also becomes function of drain to source voltage ''V''DS. As we increase the ''V''DS, the depletion regions increase in size, and a considerable amount of charge is depleted by the ''V''DS. The gate voltage required to form the channel is then lowered, and thus, the ''V''T decreases with an increase in ''V''DS. This effect is called drain induced barrier lowering (DIBL). ; Lower output resistance: For analog operation, good gain requires a high MOSFET output impedance, which is to say, the MOSFET current should vary only slightly with the applied drain-to-source voltage. As devices are made smaller, the influence of the drain competes more successfully with that of the gate due to the growing proximity of these two electrodes, increasing the sensitivity of the MOSFET current to the drain voltage. To counteract the resulting decrease in output resistance, circuits are made more complex, either by requiring more devices, for example the cascode and cascade amplifiers, or by feedback circuitry using operational amplifiers, for example a circuit like that in the adjacent figure. ; Lower transconductance: The transconductance of the MOSFET decides its gain and is proportional to hole or electron mobility (depending on device type), at least for low drain voltages. As MOSFET size is reduced, the fields in the channel increase and the dopant impurity levels increase. Both changes reduce the carrier mobility, and hence the transconductance. As channel lengths are reduced without proportional reduction in drain voltage, raising the electric field in the channel, the result is velocity saturation of the carriers, limiting the current and the transconductance. ; Interconnect capacitance: Traditionally, switching time was roughly proportional to the gate capacitance of gates. However, with transistors becoming smaller and more transistors being placed on the chip, capacitance, interconnect capacitance (the capacitance of the metal-layer connections between different parts of the chip) is becoming a large percentage of capacitance. Signals have to travel through the interconnect, which leads to increased delay and lower performance. ; Heat production: The ever-increasing density of MOSFETs on an integrated circuit creates problems of substantial localized heat generation that can impair circuit operation. Circuits operate more slowly at high temperatures, and have reduced reliability and shorter lifetimes. Heat sinks and other cooling devices and methods are now required for many integrated circuits including microprocessors. Power MOSFETs are at risk of thermal runaway. As their on-state resistance rises with temperature, if the load is approximately a constant-current load then the power loss rises correspondingly, generating further heat. When the heatsink is not able to keep the temperature low enough, the junction temperature may rise quickly and uncontrollably, resulting in destruction of the device. ; Process variations: With MOSFETs becoming smaller, the number of atoms in the silicon that produce many of the transistor's properties is becoming fewer, with the result that control of dopant numbers and placement is more erratic. During chip manufacturing, random process variations affect all transistor dimensions: length, width, junction depths, oxide thickness ''etc.'', and become a greater percentage of overall transistor size as the transistor shrinks. The transistor characteristics become less certain, more statistical. The random nature of manufacture means we do not know which particular example MOSFETs actually will end up in a particular instance of the circuit. This uncertainty forces a less optimal design because the design must work for a great variety of possible component MOSFETs. See Process variation (semiconductor), process variation, Design for manufacturability (IC), design for manufacturability, reliability engineering, and statistical process control. ; Modeling challenges: Modern ICs are computer-simulated with the goal of obtaining working circuits from the very first manufactured lot. As devices are miniaturized, the complexity of the processing makes it difficult to predict exactly what the final devices look like, and modeling of physical processes becomes more challenging as well. In addition, microscopic variations in structure due simply to the probabilistic nature of atomic processes require statistical (not just deterministic) predictions. These factors combine to make adequate simulation and "right the first time" manufacture difficult. A related scaling rule is Edholm's law. In 2004, Phil Edholm observed that the bandwidth (signal processing), bandwidth of telecommunication networks (including the Internet) is doubling every 18 months. Over the course of several decades, the bandwidths of communication networks has risen from bits per second to terabit per second, terabits per second. The rapid rise in telecommunication bandwidth is largely due to the same MOSFET scaling that enables Moore's law, as telecommunication networks are built from MOSFETs.


Timeline


See also

* BSIM * ggNMOS * High electron mobility transistor * Polysilicon depletion effect * Quantum Hall effect * Transistor model * Power MOSFET#Body diode, Intrinsic diode


References


External links


How Semiconductors and Transistors Work (MOSFETs)
WeCanFigureThisOut.org * * * * * A Flash slide showing the fabricating process of a MOSFET in detail * * * * * * * * * * * {{Authority control MOSFETs, 1959 introductions 1960 introductions 20th-century inventions Arab inventions Digital electronics Egyptian inventions Integrated circuits South Korean inventions Transistor amplifiers Transistor types