what is the capacitance component of MOSFET?

[W_Heisenberg]

I think MOSFET capacitance:

gate capacitance: overlap and channel

diffusion capacitance: n or p diffusion

is this correct?

 

[Hamid.Kiumarsi]

If by gate capacitance you mean gate-bulk capacitance then the gate capacitance consists of series combination of oxide capacitance and depletion capacitance.
We only have gate-bulk capacitance when device is off. In saturation and triode regions this capacitance is neglected because inversion layer shields the bulk.