A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a semiconductor device that is commonly used in power electronics. It works by modulating charge concentration between a gate electrode, which is insulated from other device regions by an oxide layer, and a body region. Depending on whether it is an n-channel or p-channel MOSFET, the source and drain regions have either n+ or p+ doping while the body has the opposite doping. Applying a voltage to the gate can turn the channel between source and drain on or off to allow or prevent current flow. MOSFETs can be made with silicon on insulator or other semiconductor materials.

1. Metal Oxide Semiconductor Field Effect Transistor M.S.P.V.L Polytechnic College, Pavoorchatram.

2. MOSFET Circuit

3. MOSFET Symbol Circuit

4. Introduction A MOSFET ( Metal Oxide Semiconductor Field Effect Transistor ) is a semiconductor device. A MOSFET is most commonly used in the field of power electronics. A semiconductor is made of manufactured material that acts neither like a insulator nor a conductor.

5. Structure of MOSFET

6. Schematic structure of MOSFET

7. Working principle of MOSFET A metal–oxide–semiconductor field-effect transistor (MOSFET) is based on the modulation of charge concentration by a MOS capacitance between a body electrode and a gate electrode located above the body and insulated from all other device regions by a gate dielectric layer which in the case of a MOSFET is an oxide, such as silicon dioxide .

8. Working principle of MOSFET If dielectrics other than an oxide such as silicon dioxide (often referred to as oxide) are employed the device may be referred to as a metal–insulator–semiconductor FET (MISFET). Compared to the MOS capacitor, the MOSFET includes two additional terminals ( source and drain ), each connected to individual highly doped regions that are separated by the body region.

9. N and P channel of MOSFET

10. N and P channel of MOSFET If the MOSFET is an n-channel or nMOS FET , then the source and drain are 'n+' regions and the body is a 'p' region. If the MOSFET is a p-channel or pMOS FET , then the source and drain are 'p+' regions and the body is a 'n' region.

11. Cross section of NMOS with channel- OFF state

12. Cross section of NMOS without channel- OFF state

13. When a negative gate-source voltage (positive source-gate) is applied, it creates a p-channel at the surface of the n region , analogous to the n-channel case, but with opposite polarities of charges and voltages. When a voltage less negative than the threshold value (a negative voltage for p-channel) is applied between gate and source, the channel disappears and only a very small sub threshold current can flow between the source and the drain . Working principle of MOSFET

14. Working principle of MOSFET

15. The device may comprise a Silicon On Insulator (SOI) device in which a Buried Oxide (BOX) is formed below a thin semiconductor layer. If the channel region between the gate dielectric and a Buried Oxide (BOX) region is very thin, the very thin channel region is referred to as an Ultra Thin Channel (UTC) region with the source and drain regions formed on either side thereof in and/or above the thin semiconductor layer. Working principle of MOSFET

16. Alternatively, the device may comprise a Semiconductor On Insulator (SEMOI) device in which semiconductors other than silicon are employed. When the source and drain regions are formed above the channel in whole or in part, they are referred to as Raised Source/Drain (RSD) regions Working principle of MOSFET

17. The End …… Thank You ……