Small-signal substrate resistance effect in RF CMOS identified through device simulations

An anomalous dip in the measured s/sub 22/ characteristic, as well as a decrease in the output resistance, of MOS devices for rf applications was found to be a pure ac effect caused by the small-signal substrate transconductance. The study of the ac characteristics of multifinger transistors in rf applications with a high-resistivity substrate also puts a question mark on the possibility of achieving fully scalable models, considering the observed ac substrate effect.