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{{short description|Type of transistor}}
[[File:FET cross section.svg|thumb|300px|Cross-sectional view of a MOSFET type field-effect transistor, showing ''source'', ''gate'' and ''drain'' terminals, and insulating oxide layer.]]
The '''field-effect transistor''' ('''FET''') is a type of [[transistor]] that uses an [[electric field]] to control the [[Electric current|current]] through a [[semiconductor]].
FETs are also known as '''unipolar transistors''' since they involve single-carrier-type operation. That is, FETs use either [[electron]]s (n-channel) or [[hole (semiconductor)|hole]]s (p-channel) as [[charge carrier]]s in their operation, but not both. Many different types of field effect transistors exist. Field effect transistors generally display very [[High impedance|high input impedance]] at low frequencies. The most widely used field-effect transistor is the [[MOSFET]]
==History==
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[[File:Julius Edgar Lilienfeld (1881-1963).jpg|thumb|144px|[[Julius Edgar Lilienfeld]], who proposed the concept of a field-effect transistor in 1925.]]
The concept of a field-effect transistor (FET) was first patented by the Austro-Hungarian born physicist [[Julius Edgar Lilienfeld]] in 1925<ref>Lilienfeld, J.E. [https://pdfpiw.uspto.gov/.piw?Docid=01745175 "Method and apparatus for controlling electric current"] {{Webarchive|url=https://web.archive.org/web/20220409014726/https://pdfpiw.uspto.gov/.piw?Docid=01745175 |date=2022-04-09 }} US Patent no. 1,745,175 (filed: 8 October 1926 ; issued: 28 January 1930).</ref><ref>{{patent|CA|272437|"Electric current control mechanism", first filed in Canada on October 22, 1925}}</ref> and by [[Oskar Heil]] in 1934, but they were unable to build a working practical [[semiconductor device|semiconducting device]] based on the concept. The [[transistor]] effect was later observed and explained by [[John Bardeen]] and [[Walter Houser Brattain]] while working under [[William Shockley]] at [[Bell Labs]] in 1947, shortly after the 17-year patent expired. Shockley initially attempted to build a working FET by trying to modulate the conductivity of a [[semiconductor]], but was unsuccessful, mainly due to problems with the [[surface states]], the [[dangling bond]], and the [[germanium]] and [[copper]] compound materials. In the course of trying to understand the mysterious reasons behind their failure to build a working FET, it led to Bardeen and Brattain instead inventing the [[point-contact transistor]] in 1947, which was followed by Shockley's [[bipolar junction transistor]] in 1948.<ref name="Lee">{{cite book |last1=Lee |first1=Thomas H. |title=The Design of CMOS Radio-Frequency Integrated Circuits |date=2003 |publisher=[[Cambridge University Press]] |isbn=978-1-139-64377-1 |url=https://web.stanford.edu/class/archive/ee/ee214/ee214.1032/Handouts/HO2.pdf |access-date=2019-07-20 |archive-date=2019-12-09 |archive-url=https://web.archive.org/web/20191209032130/https://web.stanford.edu/class/archive/ee/ee214/ee214.1032/Handouts/HO2.pdf }}</ref><ref name="Puers">{{cite book |last1=Puers |first1=Robert |last2=Baldi |first2=Livio |last3=Voorde |first3=Marcel Van de |last4=Nooten |first4=Sebastiaan E. van |title=Nanoelectronics: Materials, Devices, Applications, 2 Volumes |date=2017 |publisher=[[John Wiley & Sons]] |isbn=978-3-527-34053-8 |page=14 |url=https://books.google.com/books?id=JOqVDgAAQBAJ&pg=PA14}}</ref>
The first FET device to be successfully built was the [[JFET|junction field-effect transistor]] (JFET).<ref name="Lee"/> A JFET was first patented by [[Heinrich Welker]] in 1945.<ref>{{cite book |title=The Physics of Semiconductors|author=Grundmann, Marius|isbn=978-3-642-13884-3 |publisher=Springer-Verlag|year=2010}}</ref> The [[static induction transistor]] (SIT), a type of JFET with a short channel, was invented by Japanese engineers [[Jun-ichi Nishizawa]] and Y. Watanabe in 1950. Following Shockley's theoretical treatment on the JFET in 1952, a working practical JFET was built by [[George C. Dacey]] and [[Ian Munro Ross|Ian M. Ross]] in 1953.<ref name=sit>{{cite book|first=Jun-Ichi |last=Nishizawa|editor-first1=Roland|editor-last1=Sittig|editor-first2=P.|editor-last2=Roggwiller|publisher=Springer|chapter=Junction Field-Effect Devices|title=Semiconductor Devices for Power Conditioning|year=1982|pages=241–272|doi=10.1007/978-1-4684-7263-9_11|isbn=978-1-4684-7265-3}}</ref> However, the JFET still had issues affecting [[junction transistor]]s in general.<ref name="Moskowitz">{{cite book |last1=Moskowitz |first1=Sanford L. |title=Advanced Materials Innovation: Managing Global Technology in the 21st century |date=2016 |publisher=[[John Wiley & Sons]] |isbn=978-0-470-50892-3 |page=168 |url=https://books.google.com/books?id=2STRDAAAQBAJ&pg=PA168}}</ref> Junction transistors were relatively bulky devices that were difficult to manufacture on a [[mass-production]] basis, which limited them to a number of specialised applications. The insulated-gate field-effect transistor (IGFET) was theorized as a potential alternative to junction transistors, but researchers were unable to build working IGFETs, largely due to the troublesome surface state barrier that prevented the external [[electric field]] from penetrating into the material.<ref name="Moskowitz"/> By the mid-1950s, researchers had largely given up on the FET concept, and instead focused on [[bipolar junction transistor]] (BJT) technology.<ref name="triumph">{{cite web |title=The Foundation of Today's Digital World: The Triumph of the MOS Transistor |url=https://www.youtube.com/watch?v=q6fBEjf9WPw |publisher=[[Computer History Museum]] |access-date=21 July 2019 |date=13 July 2010}}</ref>
The foundations of MOSFET technology were laid down by the work of [[William Shockley]], [[John Bardeen]] and [[Walter Brattain]]. Shockley independently envisioned the FET concept in 1945, but he was unable to build a working device. The next year Bardeen explained his failure in terms of [[surface states]]. Bardeen applied the theory of surface states on semiconductors (previous work on surface states was done by Shockley in 1939 and [[Igor Tamm]] in 1932) and realized that the external field was blocked at the surface because of
After Bardeen's surface state theory the trio tried to overcome the effect of surface states. In late 1947, Robert Gibney and Brattain suggested the use of electrolyte placed between metal and semiconductor to overcome the effects of surface states. Their FET device worked, but amplification was poor. Bardeen went further and suggested to rather focus on the conductivity of the inversion layer. Further experiments led them to replace electrolyte with a solid oxide layer in the hope of getting better results. Their goal was to penetrate the oxide layer and get to the inversion layer. However, Bardeen suggested they switch from [[silicon]] to [[germanium]] and in the process their oxide got inadvertently washed off. They stumbled upon a completely different transistor, the [[point-contact transistor]]. [[Lillian Hoddeson]] argues that "had Brattain and Bardeen been working with silicon instead of germanium they would have stumbled across a successful field effect transistor".<ref name="b1" /><ref name="Camezind">{{cite book | author=Hans Camenzind | author-link=Hans Camenzind | title=Designing Analog Chips | date=2005 | url=http://www.designinganalogchips.com/}}</ref><ref>{{cite book | title=ULSI Science and Technology/1997 | url= https://books.google.com/books?id=I8_O1anzKpsC | date=1997 |
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By the end of the first half of the 1950s, following theoretical and experimental work of Bardeen, Brattain, Kingston, Morrison and others, it became more clear that there were two types of surface states. Fast surface states were found to be associated with the bulk and a semiconductor/oxide interface. Slow surface states were found to be associated with the oxide layer because of [[adsorption]] of atoms, molecules and ions by the oxide from the ambient. The latter were found to be much more numerous and to have much longer [[relaxation (physics)|relaxation time]]s. At the time [[Philo Farnsworth]] and others came up with various methods of producing atomically clean semiconductor surfaces.
In 1955, [[Carl Frosch]] and Lincoln Derrick accidentally covered the surface of silicon [[wafer (electronics)|wafer]] with a layer of [[silicon dioxide]].<ref name="auto">{{Cite patent|number=US2802760A|title=Oxidation of semiconductive surfaces for controlled diffusion|gdate=1957-08-13|invent1=Lincoln|invent2=Frosch|inventor1-first=Derick|inventor2-first=Carl J.|url=https://patents.google.com/patent/US2802760A}}</ref> They showed that oxide layer prevented certain dopants into the silicon wafer, while allowing for others, thus discovering the [[Passivation (chemistry)|passivating]] effect of [[Thermal oxidation|oxidation]] on the semiconductor surface. Their further work demonstrated how to etch small openings in the oxide layer to diffuse dopants into selected areas of the 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 [[semiconductor device fabrication|fabrication]] of MOSFET devices.<ref name=":1">{{Cite journal |last1=Frosch |first1=C. J. |last2=Derick |first2=L |date=1957 |title=Surface Protection and Selective Masking during Diffusion in Silicon |url=https://iopscience.iop.org/article/10.1149/1.2428650 |journal=Journal of the Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650|url-access=subscription }}</ref> At Bell Labs, the importance of Frosch's technique was immediately realized. Results of their work circulated around Bell Labs in the form of BTL memos before being published in 1957. At [[Shockley Semiconductor Laboratory|Shockley Semiconductor]], Shockley had circulated the preprint of their article in December 1956 to all his senior staff, including [[Jean Hoerni]].<ref name="Moskowitz" /><ref>{{cite book |author1=Christophe Lécuyer |author2=David C. Brook |author3=Jay Last | title=Makers of the Microchip: A Documentary History of Fairchild Semiconductor | date=2010 | pages=62–63 |publisher=MIT Press | isbn=978-0-262-01424-3 | url=https://books.google.com/books?id=LaZpUpkG70QC&pg=PA62}}</ref><ref>{{cite book |last1=Claeys |first1=Cor L. |title=ULSI Process Integration III: Proceedings of the International Symposium |date=2003 |publisher=[[The Electrochemical Society]] |isbn=978-1-56677-376-8 |pages=27–30 | url=https://books.google.com/books?id=bu22JNYbE5MC&pg=PA27}}</ref>
In 1955, [[Ian Munro Ross]] filed a patent for a [[FeFET]] or MFSFET. Its structure was like that of a modern inversion channel MOSFET, but ferroelectric material was used as a dielectric/insulator instead of oxide. He envisioned it as a form of memory, years before the [[floating gate MOSFET]]. In February 1957, [[J. Torkel Wallmark|John Wallmark]] filed a patent for [[thin-film transistor|FET]] in which [[germanium monoxide]] was used as a gate dielectric, but he didn't pursue the idea. In his other patent filed the same year he described a [[multigate device|double gate]] FET. In March 1957, in his laboratory notebook, Ernesto Labate, a research scientist at [[Bell Labs]], conceived of a device similar to the later proposed MOSFET, although Labate's device didn't explicitly use [[silicon dioxide]] as an insulator.<ref>{{cite book |last1=Lojek |first1=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=Springer Science & Business Media |isbn=978-3-540-34258-8 |page=324}}</ref><ref>{{cite book | author=Stefan Ferdinand Müller | title=Development of HfO2-Based Ferroelectric Memories for Future CMOS Technology Nodes | year=2016 | publisher=BoD – Books on Demand | isbn=978-3-7392-4894-3}}</ref><ref>{{cite book |author1=B.G Lowe |author2=R.A. Sareen | title=Semiconductor X-Ray Detectors | date=2013 |publisher=CRC Press | isbn=978-1-4665-5401-6 }}</ref><ref name="Bassett22">{{cite book |last1=Bassett |first1=Ross Knox |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=Johns Hopkins University Press |isbn=978-0-8018-8639-3 |page=22 |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA22}}</ref>
In 1955, [[Carl Frosch]] and Lincoln Derrick accidentally grew a layer of silicon dioxide over the silicon wafer, for which they observed [[surface passivation]] effects.<ref name=":0">{{Cite journal |last1=Huff |first1=Howard |last2=Riordan |first2=Michael |date=2007-09-01 |title=Frosch and Derick: Fifty Years Later (Foreword) |url=https://iopscience.iop.org/article/10.1149/2.F02073IF |journal=The Electrochemical Society Interface |volume=16 |issue=3 |pages=29 |doi=10.1149/2.F02073IF |issn=1064-8208}}</ref><ref
===Metal–oxide–semiconductor FET (MOSFET)===
{{Main|MOSFET}}
▲In 1955, [[Carl Frosch]] and Lincoln Derrick accidentally grew a layer of silicon dioxide over the silicon wafer, for which they observed [[surface passivation]] effects.<ref name=":0">{{Cite journal |last1=Huff |first1=Howard |last2=Riordan |first2=Michael |date=2007-09-01 |title=Frosch and Derick: Fifty Years Later (Foreword) |url=https://iopscience.iop.org/article/10.1149/2.F02073IF |journal=The Electrochemical Society Interface |volume=16 |issue=3 |pages=29 |doi=10.1149/2.F02073IF |issn=1064-8208}}</ref><ref>{{Cite patent|number=US2802760A|title=Oxidation of semiconductive surfaces for controlled diffusion|gdate=1957-08-13|invent1=Lincoln|invent2=Frosch|inventor1-first=Derick|inventor2-first=Carl J.|url=https://patents.google.com/patent/US2802760A}}</ref> By 1957 Frosch and Derrick, using masking and predeposition, were able to manufacture silicon dioxide transistors and showed that silicon dioxide insulated, protected silicon wafers and prevented dopants from diffusing into the wafer.<ref name=":0" /><ref>{{Cite journal |last1=Frosch |first1=C. J. |last2=Derick |first2=L |date=1957 |title=Surface Protection and Selective Masking during Diffusion in Silicon |url=https://iopscience.iop.org/article/10.1149/1.2428650 |journal=Journal of the Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650}}</ref> J.R. Ligenza and W.G. Spitzer studied the mechanism of thermally grown oxides and fabricated a high quality Si/[[Silicon dioxide|SiO<sub>2</sub>]] stack in 1960.<ref>{{Cite journal |last1=Ligenza |first1=J. R. |last2=Spitzer |first2=W. G. |date=1960-07-01 |title=The mechanisms for silicon oxidation in steam and oxygen |url=https://linkinghub.elsevier.com/retrieve/pii/0022369760902195 |journal=Journal of Physics and Chemistry of Solids |volume=14 |pages=131–136 |doi=10.1016/0022-3697(60)90219-5 |bibcode=1960JPCS...14..131L |issn=0022-3697}}</ref><ref name="Deal">{{cite book |last1=Deal |first1=Bruce E. |title=Silicon materials science and technology |date=1998 |publisher=[[The Electrochemical Society]] |isbn=978-1566771931 |page=183 |chapter=Highlights Of Silicon Thermal Oxidation Technology |chapter-url=https://books.google.com/books?id=cr8FPGkiRS0C&pg=PA183}}</ref><ref>{{cite book |last1=Lojek |first1=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=Springer Science & Business Media |isbn=978-3540342588 |page=322}}</ref>
Following this research, [[Mohamed Atalla]] and [[Dawon Kahng]] proposed a silicon MOS transistor in 1959<ref name="Bassett222">{{cite book |last1=Bassett |first1=Ross Knox |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA22 |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=[[Johns Hopkins University Press]] |isbn=978-0-8018-8639-3 |pages=22–23}}</ref> and successfully demonstrated a working MOS device with their Bell Labs team in 1960.<ref>{{cite journal |last1=Atalla |first1=M. |author1-link=Mohamed Atalla |last2=Kahng |first2=D. |author2-link=Dawon Kahng |date=1960 |title=Silicon-silicon dioxide field induced surface devices |journal=IRE-AIEE Solid State Device Research Conference}}</ref><ref>{{cite journal |title=1960 – Metal Oxide Semiconductor (MOS) Transistor Demonstrated |url=https://www.computerhistory.org/siliconengine/metal-oxide-semiconductor-mos-transistor-demonstrated/ |journal=The Silicon Engine |publisher=[[Computer History Museum]] |access-date=2023-01-16}}</ref> Their team included E. E. LaBate and E. I. Povilonis who fabricated the device; M. O. Thurston, L. A. D’Asaro, and J. R. Ligenza who developed the diffusion processes, and H. K. Gummel and R. Lindner who characterized the device.<ref>{{Cite journal |last=KAHNG |first=D. |date=1961 |title=Silicon-Silicon Dioxide Surface Device |url=https://doi.org/10.1142/9789814503464_0076 |journal=Technical Memorandum of Bell Laboratories|pages=583–596 |doi=10.1142/9789814503464_0076 |isbn=978-981-02-0209-5 |url-access=subscription }}</ref><ref>{{Cite book |last=Lojek |first=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=Springer-Verlag Berlin Heidelberg |isbn=978-3-540-34258-8 |___location=Berlin, Heidelberg |page=321}}</ref>
With its [[MOSFET scaling|high scalability]],<ref>{{cite journal |last1=Motoyoshi |first1=M. |s2cid=29105721 |title=Through-Silicon Via (TSV) |journal=Proceedings of the IEEE |date=2009 |volume=97 |issue=1 |pages=43–48 |doi=10.1109/JPROC.2008.2007462 |issn=0018-9219}}</ref> and much lower power consumption and higher density than bipolar junction transistors,<ref>{{cite news |title=Transistors Keep Moore's Law Alive |url=https://www.eetimes.com/author.asp?section_id=36&doc_id=1334068 |access-date=18 July 2019 |work=[[EETimes]] |date=12 December 2018}}</ref> the MOSFET made it possible to build [[Large scale integration|high-density]] integrated circuits.<ref>{{cite web |title=Who Invented the Transistor? |url=https://www.computerhistory.org/atchm/who-invented-the-transistor/ |website=[[Computer History Museum]] |date=4 December 2013 |access-date=20 July 2019}}</ref> The MOSFET is also capable of handling higher power than the JFET.<ref>{{cite book |last1=Duncan |first1=Ben |title=High Performance Audio Power Amplifiers |date=1996 |publisher=[[Elsevier]] |isbn=978-0-08-050804-7 |url=https://books.google.com/books?id=-5UPyE6dcWgC&pg=PA177 |page=177}}</ref> The MOSFET was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses.<ref name="Moskowitz" /> The MOSFET thus became the most common type of transistor in computers, electronics,<ref name="kahng">{{cite web |title=Dawon Kahng |url=https://www.invent.org/inductees/dawon-kahng |access-date=27 June 2019 |website=[[National Inventors Hall of Fame]]}}</ref> and [[communications technology]] (such as [[smartphones]]).<ref name="uspto">{{cite web |title=Remarks by Director Iancu at the 2019 International Intellectual Property Conference |url=https://www.uspto.gov/about-us/news-updates/remarks-director-iancu-2019-international-intellectual-property-conference |website=[[United States Patent and Trademark Office]] |date=June 10, 2019 |access-date=20 July 2019 |archive-date=17 December 2019 |archive-url=https://web.archive.org/web/20191217200937/https://www.uspto.gov/about-us/news-updates/remarks-director-iancu-2019-international-intellectual-property-conference |url-status=dead }}</ref> The [[US Patent and Trademark Office]] calls it a "groundbreaking invention that transformed life and culture around the world".<ref name="uspto" />
In 1948, Bardeen and Brattain patented the progenitor of MOSFET, an insulated-gate FET (IGFET) with an inversion layer. Their patent and the concept of an inversion layer, forms the basis of CMOS technology today.<ref>{{cite book |author=Howard R. Duff |title=AIP Conference Proceedings |date=2001 |volume=550 |pages=3–32 |chapter=John Bardeen and transistor physics |doi=10.1063/1.1354371 |doi-access=free}}</ref> [[CMOS]] (complementary MOS), a semiconductor device fabrication process for MOSFETs, was developed by [[Chih-Tang Sah]] and [[Frank Wanlass]] at [[Fairchild Semiconductor]] in 1963.<ref name="computerhistory1963">{{cite web |title=1963: Complementary MOS Circuit Configuration is Invented |url=https://www.computerhistory.org/siliconengine/complementary-mos-circuit-configuration-is-invented/ |website=[[Computer History Museum]] |access-date=6 July 2019}}</ref><ref>{{US patent|3102230}}, filed in 1960, issued in 1963</ref> The first report of a [[floating-gate MOSFET]] was made by Dawon Kahng and [[Simon Sze]] in 1967.<ref>D. Kahng and S. M. Sze, "A floating gate and its application to memory devices", ''The Bell System Technical Journal'', vol. 46, no. 4, 1967, pp. 1288–1295</ref> The concept of a [[double-gate]] [[thin-film transistor]] (TFT) was proposed by H. R. Farrah ([[Bendix Corporation]]) and R. F. Steinberg in 1967.<ref name="FarrahSteinberg">{{cite journal |last1=Farrah |first1=H. R. |last2=Steinberg |first2=R. F. |date=February 1967 |title=Analysis of double-gate thin-film transistor |journal=IEEE Transactions on Electron Devices |volume=14 |issue=2 |pages=69–74 |bibcode=1967ITED...14...69F |doi=10.1109/T-ED.1967.15901}}</ref> A [[double-gate]] MOSFET was first demonstrated in 1984 by [[Electrotechnical Laboratory]] researchers Toshihiro Sekigawa and Yutaka Hayashi.<ref>{{cite book |last1=Colinge |first1=J.P. |title=FinFETs and Other Multi-Gate Transistors |date=2008 |publisher=Springer Science & Business Media |isbn=978-0-387-71751-7 |page=11 |url=https://books.google.com/books?id=t1ojkCdTGEEC&pg=PA11}}</ref><ref>{{cite journal |last1=Sekigawa |first1=Toshihiro |last2=Hayashi |first2=Yutaka |title=Calculated threshold-voltage characteristics of an XMOS transistor having an additional bottom gate |journal=Solid-State Electronics |date=1 August 1984 |volume=27 |issue=8 |pages=827–828 |doi=10.1016/0038-1101(84)90036-4 |bibcode=1984SSEle..27..827S |issn=0038-1101}}</ref> [[FinFET]] (fin field-effect transistor), a type of 3D non-planar [[Multigate device|multi-gate]] MOSFET, originated from the research of Digh Hisamoto and his team at [[Hitachi|Hitachi Central Research Laboratory]] in 1989.<ref>{{cite web |title=IEEE Andrew S. Grove Award Recipients |url=https://www.ieee.org/about/awards/bios/grove-recipients.html |archive-url=https://web.archive.org/web/20180909112404/https://www.ieee.org/about/awards/bios/grove-recipients.html |url-status=dead |archive-date=September 9, 2018 |website=[[IEEE Andrew S. Grove Award]] |publisher=[[Institute of Electrical and Electronics Engineers]] |access-date=4 July 2019}}</ref><ref>{{cite web |title=The Breakthrough Advantage for FPGAs with Tri-Gate Technology |url=https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/wp/wp-01201-fpga-tri-gate-technology.pdf |publisher=[[Intel]] |year=2014 |access-date=4 July 2019}}</ref>
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The FET's three terminals are:<ref name=millman>{{cite book|author=Jacob Millman|title=Electronic devices and circuits|year=1985|pages=384–385|publisher=McGraw-Hill|___location=Singapore|isbn=978-0-07-085505-2}}</ref>
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==More about terminals==
[[File:Lateral mosfet.svg|thumbnail|Cross section of an n-type MOSFET]]
All FETs have ''source'', ''drain'', and ''gate'' terminals that correspond roughly to the ''emitter'', ''collector'', and ''base'' of [[bipolar junction transistor|BJT]]s. Most FETs have a fourth terminal called the ''body'', ''base'', ''bulk'', or ''[[substrate (electronics)|substrate]].'' This fourth terminal serves to [[biasing (electronics)|bias]] the transistor into operation; it is rare to make non-trivial use of the body terminal in circuit designs, but its presence is important when setting up the [[integrated circuit layout|physical layout]] of an [[integrated circuit]]. The size of the gate,
The names of the terminals refer to their functions. The gate terminal may be thought of as controlling the opening and closing of a physical gate. This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. Electron-flow from the source terminal towards the drain terminal is influenced by an applied voltage. The body simply refers to the bulk of the semiconductor in which the gate, source and drain lie. Usually the body terminal is connected to the highest or lowest voltage within the circuit, depending on the type of the FET. The body terminal and the source terminal are sometimes connected together since the source is often connected to the highest or lowest voltage within the circuit, although there are several uses of FETs which do not have such a configuration, such as [[transmission gate]]s and [[cascode]] circuits.
Unlike BJTs, the vast majority of FETs are electrically symmetrical. The source and drain terminals can thus be interchanged in practical circuits with no change in operating characteristics or function.
===Effect of gate voltage on current===
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**The DGMOSFET ([[dual-gate MOSFET]]) or DGMOS, a MOSFET with two insulated gates.
**The IGBT ([[insulated-gate bipolar transistor]]) is a device for power control. It has a structure akin to a MOSFET coupled with a bipolar-like main conduction channel. These are commonly used for the 200–3000 V drain-to-source voltage range of operation. [[Power MOSFET]]s are still the device of choice for drain-to-source voltages of 1 to 200 V.
**The JLNT ([[
**The MNOS ([[metal–nitride–oxide–semiconductor transistor]]) utilizes a nitride-oxide layer [[Electrical insulation|insulator]] between the gate and the body.
**The [[ISFET]] (ion-sensitive field-effect transistor) can be used to measure ion concentrations in a solution; when the ion concentration (such as H<sup>+</sup>, see [[pH electrode]]) changes, the current through the transistor will change accordingly.
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*The GFET is a highly sensitive graphene-based field effect transistor used as [[biosensor]]s and [[Sensor#Chemical sensor|chemical sensors]]. Due to the 2 dimensional structure of graphene, along with its physical properties, GFETs offer increased sensitivity, and reduced instances of 'false positives' in sensing applications<ref>{{cite web|author=Miklos, Bolza|title=What Are Graphene Field Effect Transistors (GFETs)?|url=https://www.graphenea.com/pages/what-are-graphene-field-effect-transistors-gfets|website=Graphenea|access-date=14 January 2019}}</ref>
*The [[Fe FET]] uses a [[ferroelectric]] between the gate, allowing the transistor to retain its state in the absence of bias - such devices may have application as [[non-volatile memory]].
* VTFET, or [[
==Advantages==
Field-effect transistors have high gate-to-drain current resistance, of the order of 100 MΩ or more, providing a high degree of isolation between control and flow. Because base current noise will increase with shaping time{{clarify|date=December 2021}},<ref>
Because the FETs are controlled by gate charge, once the gate is closed or open, there is no additional power draw, as there would be with a [[bipolar junction transistor]] or with non-latching [[relay]]s in some states. This allows extremely low-power switching, which in turn allows greater miniaturization of circuits because heat dissipation needs are reduced compared to other types of switches.
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FET is commonly used as an amplifier. For example, due to its large input resistance and low output resistance, it is effective as a buffer in [[common-drain]] (source follower) configuration.
==Source-gated transistor==
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==References==
{{Reflist|30em}}
==External links==
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