Editing MOSFET (section)

{{Short description|Type of field-effect transistor}}
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[[file:D2PAK.JPG|thumb|upright=1.3|Two [[power transistor|power MOSFETs]] in [[D2PAK]] [[surface-mount package]]s. Operating as switches, each of these components can sustain a blocking voltage of 120{{nbsp}}[[volts|V]] in the ''off'' state, and can conduct a con&shy;ti&shy;nuous current of 30&nbsp;[[amperes|A]] in the ''on'' state, dissipating up to about 100&nbsp;[[watt|W]] and controlling a load of over 2000&nbsp;W. A [[matchstick]] is pictured for scale.]]

In [[electronics]], the '''metal–oxide–semiconductor field-effect transistor''' ('''MOSFET''', '''MOS-FET''', '''MOS FET''', or '''MOS transistor''') is a type of [[field-effect transistor]] (FET), most commonly fabricated by the [[thermal oxidation|controlled oxidation]] of [[silicon]]. It has an insulated gate, the [[voltage]] of which determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic [[signal]]s. The term ''metal–insulator–semiconductor field-effect transistor'' (''MISFET'') is almost synonymous with ''MOSFET''. Another near-synonym is ''insulated-gate field-effect transistor'' (''IGFET'').

The main advantage of a MOSFET is that it requires almost no input current to control the load current under steady-state or low-frequency conditions, especially compared to bipolar junction transistors (BJTs). However, at high frequencies or when switching rapidly, a MOSFET may require significant current to charge and discharge its gate capacitance. In an ''enhancement mode'' MOSFET, voltage applied to the gate terminal increases the conductivity of the device. In ''depletion mode'' transistors, voltage applied at the gate reduces the conductivity.<ref name="depletion">{{cite web |title=D-MOSFET OPERATION AND BIASING |url=https://massless.info/images/CLASS%2025.pdf |archive-url=https://web.archive.org/web/20221022122055/https://massless.info/images/CLASS%2025.pdf |archive-date=2022-10-22 |url-status=live}}</ref>

The "metal" in the name MOSFET is sometimes a [[misnomer]], because the gate material can be a layer of [[polysilicon]] (polycrystalline silicon). Similarly, "oxide" in the name can also be a misnomer, as different dielectric materials are used with the aim of obtaining strong channels with smaller applied voltages.

The MOSFET is by far the most common transistor in [[digital circuit|digital]] circuits, as billions may be included in a [[memory chip]] or [[microprocessor]]. As MOSFETs can be made with either p-type or n-type semiconductors, complementary pairs of MOS transistors can be used to make switching circuits with very low power consumption, in the form of [[CMOS logic]].

[[file:MOSFET functioning body.svg|thumb|upright=1.3|A cross-section through an nMOSFET when the gate voltage ''V''<sub>GS</sub> is below the threshold for making a conductive channel; there is little or no conduction between the terminals drain and source; 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 (yellow), which allows electrons to flow between the ''n''-doped terminals; the switch is on.]]