MOSFET Transistor

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A MOSFET Transistor is a transistor where a voltage on the oxide-insulated gate electrode can induce a conducting channel between a source connector and a drain connector.



    • The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925. Twenty five years later, when Bell Telephone attempted to patent the Junction Transistor, they found Lilienfeld already holding a patent which was worded in a way that would include all types of transistors. Bell Labs was able to work out an agreement with Lilienfeld, who was still alive at that time. (It is not known if they paid him money or not.) It was at that time, the Bell Labs version was given the name, Bipolar Junction Transistor, or simply Junction Transistor, and Lilienfeld's design took the name, Field Effect Transistor.

      In MOSFETs, a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain. The channel can be of n-type or p-type (see article on semiconductor devices), and is accordingly called an nMOSFET or a pMOSFET (also commonly nMOS, pMOS). It is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common.

      The 'metal' in the name is now often a misnomer because the previously metal gate material is now often a layer of polysilicon (polycrystalline silicon). Aluminium had been the gate material until the mid 1970s, when polysilicon became dominant, due to its capability to form self-aligned gates. Metallic gates are regaining popularity, since it is difficult to increase the speed of operation of transistors without metal gates.

      IGFET is a related term meaning insulated-gate field-effect transistor, and is used almost synonymously with MOSFET, being more accurate since many "MOSFETs" use a gate that is not metal and a gate insulator that is not oxide. Another synonym is MISFET for metal–insulator–semiconductor FET.