In this work, the high-frequency performance of a 0.18-mum CMOS device has been analyzed with various multi-finger layouts and biases to find the optimal condition. The optimal bias condition to maximize the cutoff frequency (f(T)) and the maximum oscillation frequency (f(max)) have been found to be equal to that required to maximize the transconductance (g(m)). At this bias condition, f(T) tends to be maximized with a small number of fingers. It has been found that f(max) strongly depends on the gate resistance. Finally, the de-embedding effects on cutoff frequency are presented.