Scaling of characteristic frequencies in RF CMOS

Device simulation of the 180-, 90-, and 65-nm CMOS generations shows that in NMOSTs, the cut-off frequency f/sub T/ and the maximum oscillation frequency f/sub max/ are roughly inversely proportional to the gate length. The voltage-gain bandwidth f/sub A/ depends only weakly on the gate length. At 40-nm gate length, f/sub T/ values of 300 GHz are predicted. For small values of the drain and source contact resistance (<10/sup -8/ /spl Omega//spl middot/cm/sup 2/), f/sub T/ can only be improved by a further reduction of the gate length. The f/sub max/ values (for zero gate resistance higher than f/sub T/) degrade strongly with increasing gate resistance. Simple approximate formulas for the dependence of f/sub T/ and f/sub A/ on the contact resistances are presented.