Impact of parasitic elements on RF performance of nanometre-scale MOSFET structures

A recently reported nanometre-scaled MOSFET structure with regrown source and drain is examined. The parasitic circuit elements are identified and quantitatively determined to estimate their impact on the transistor's RF performance. Due to the relatively large lateral parasitic capacitances from the gate electrode to the regrown source and drain regions, the current gain cut-off frequency f_T of such a transistor is optimistically estimated to be 184 GHz which is not impressive for nanoelectronic devices with an effective gate length of 30 nm. However, with the significantly reduced parasitic series resistances due to the regrown source and drain structures together with the use of the metal gate, the maximum frequency of oscillation f_max can attain to 820 GHz. This brings about an implication that device structure optimization to reduce the parasitic resistances has a dominant beneficial effect on the RF performance over the negative impact caused by the increased parasitic capacitances.