Editing MOSFET (section)

=== Dual-gate ===
[[file:FINFET MOSFET.png|thumb|upright=1.2|A [[FinFET]]]]
{{Main|Multigate device}}

The dual-gate MOSFET 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]] 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.<ref name=SOI>{{cite book |title=Frontiers in electronics: future chips : proceedings of the 2002 Workshop on Frontiers in Electronics (WOFE-02), St Croix, Virgin Islands, USA, 6–11 January 2002 |year=2002|publisher=World Scientific |chapter=Figure 12: Simplified cross section of FinFET double-gate MOSFET |isbn=978-981-238-222-1|first1=P. M.|last1= Zeitzoff |first2=J. A.|last2= Hutchby |first3=H. R.|last3= Huff |editor1-first=Yoon-Soo|editor1-last=Park |editor2-first=Michael|editor2-last=Shur |editor3-first=William|editor3-last=Tang |chapter-url=https://books.google.com/books?id=uC6h4-OEWsMC&pg=PA82 |page=82}}</ref><ref>{{cite book |title=Silicon-on-Insulator Technology and Devices |chapter=Comparison of SOI FinFETs and bulk FinFETs: Figure 2 |first1=J.-H.|last1= Lee |first2=J.-W.|last2= Lee |first3=H.-A.-R.|last3= Jung |first4=B.-K.|last4= Choi |chapter-url=https://books.google.com/books?id=OVbb42PwZysC&pg=PA102 |page=102 |publisher=The Electrochemical Society |year=2009 |isbn=978-1-56677-712-4}}</ref>