Effect of parasitic capacitances and resistances on the RF performance of nanoscale MOSFETs

The effect of parasitic capacitances and resistances on RF performance is investigated for a recently reported 30-nm transistor with regrown source and drain structure which is to reduce the access resistance in nanoscale MOSFETs. The relatively large lateral parasitic capacitances from the gate electrode to the regrown source and drain regions are quantitatively determined to estimate their impact on the transistor's RF performance. The current gain cut-off frequency fT of such a transistor is estimated to be about 320 GHz using small-signal equivalent circuit model calculations. With the significantly reduced parasitic series resistances due to the regrown source and drain structures, the maximum frequency of oscillation fmax can attain up to 530 GHz. The parasitic circuit elements are identified to have varying degree of impact on the RF performance. This brings important implication in the device design and structure optimization in nanoscale transistors for RF applications.