Editing Semiconductor device (section)

===Transistor===
{{main|Transistor}}

====Bipolar junction transistor====
[[File:Bipolar Junction Transistor NPN Structure.svg|right|thumb|180px|An n–p–n bipolar junction transistor structure]]

[[Bipolar junction transistors]] (BJTs) are formed from two p–n junctions, in either n–p–n or p–n–p configuration. The middle, or ''base'', the region between the junctions is typically very narrow. The other regions, and their associated terminals, are known as the ''emitter'' and the ''collector''. A small current injected through the junction between the base and the emitter changes the properties of the base-collector junction so that it can conduct current even though it is reverse biased. This creates a much larger current between the collector and emitter, controlled by the base-emitter current.

====Field-effect transistor====
{{main|Field-effect transistor}}

Another type of transistor, the [[field-effect transistor]] (FET), operates on the principle that semiconductor conductivity can be increased or decreased by the presence of an [[electric field]]. An electric field can increase the number of free electrons and holes in a semiconductor, thereby changing its conductivity. The field may be applied by a reverse-biased p–n junction, forming a ''junction field-effect transistor'' ([[JFET]]) or by an electrode insulated from the bulk material by an oxide layer, forming a ''metal–oxide–semiconductor field-effect transistor'' ([[MOSFET]]).

====Metal-oxide-semiconductor====
{{Main|MOSFET}}
{{See also|List of semiconductor scale examples|Transistor count}}
[[File:Threshold formation nowatermark.gif|thumb|right|400px|Operation of a [[MOSFET]] and its Id-Vg curve. At first, when no gate voltage is applied. There is no inversion electron in the channel, the device is OFF. As gate voltage increase, the inversion electron density in the channel increase, the current increases, and the device turns on.]]

The [[MOSFET|metal-oxide-semiconductor FET]] (MOSFET, or MOS transistor), a [[solid-state electronics|solid-state]] device, is by far the most used widely semiconductor device today. It accounts for at least 99.9% of all transistors, and there have been an estimated 13{{nbsp}}[[sextillion]] MOSFETs manufactured between 1960 and 2018.<ref name="computerhistory2018">{{cite web |title=13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History |url=https://www.computerhistory.org/atchm/13-sextillion-counting-the-long-winding-road-to-the-most-frequently-manufactured-human-artifact-in-history/ |date=April 2, 2018 |website=[[Computer History Museum]] |access-date=28 July 2019}}</ref>

The ''gate'' electrode is charged to produce an electric field that controls the [[electrical conductivity|conductivity]] of a "channel" between two terminals, called the ''source'' and ''drain''. Depending on the type of carrier in the channel, the device may be an ''n-channel'' (for electrons) or a ''p-channel'' (for holes) MOSFET. Although the MOSFET is named in part for its "metal" gate, in modern devices [[polysilicon]] is typically used instead.