The positive voltage also attracts electrons from the n+ source and drain regions into the channel. When electrons are reached, a channel is developed. The depletion region populated by the bound negative charges which are associated with the acceptor atoms. When we apply a repulsive force for the positive gate voltage, then the holes present beneath the oxide layer are pushed downward with the substrate. The semiconductor surface at the below oxide layer which is located between the source and drain terminal can be inverted from p-type to n-type by the application of either a positive or negative gate voltages respectively. The MOS capacitor is the main part of MOSFET. It works almost like a switch and the functionality of the device is based on the MOS capacitor. The main principle of the MOSFET device is to be able to control the voltage and current flow between the source and drain terminals. Enhancement Mode Working Principle of MOSFET When there is the maximum voltage across the gate terminal, then the device shows enhanced conductivity. When there is no voltage across the gate terminal, then the device does not conduct. Please refer to this link to know more about Depletion Mode MOSFET Enhancement Mode Whereas when the voltage across the gate terminal is either positive or negative, then the channel conductivity decreases. When there is no voltage across the gate terminal, the channel shows its maximum conductance. The MOS capacity that exists in the device is the crucial section where the entire operation is across this. It is insulated from the channel near an extremely thin layer of metal oxide. The width of the channel is controlled by the voltage on an electrode which is called the gate and it is located in between the source and the drain.

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