Physical origin of gate voltage-dependent drain–source capacitance in short-channel MOSFETs

For the first time, it is revealed that the physical origin of the gate-source voltage (V_gs)-dependent drain-source capacitance in short-channel metal-oxide semiconductor field-effect transistors (MOSFETs) comes from the depletion capacitance components between the drain and channel end in the saturation region. On the basis of this origin, it is newly found that the V_gs-dependent channel resistance should be connected in series with the drain-source capacitance to model the high-frequency (HF) response of the intrinsic output capacitance. The accuracy of an improved MOSFET model, including the channel resistance, is validated by observing the excellent agreement with the measured S-parameters in the wide range of V_gs up to 40 GHz.