P-channel versus N-channel in MOS-ICs of submicron channel lengths

Measurements of saturated currents made on numerous MOSFETs of decreasing channel lengths, show that their “conducting capability” is dropping sharply due to the effect of carrier velocity saturation and that this tendency is sharper in n-channel devices than in p-channel ones. The tendency is adequately explained using a previously reported one-dimensional model with some refinements. Simulation for the propagation delay time of ring oscillators show that the continuing drop in conducting capability of short channel devices, will eventually lead to a situation where the NMOS and the PMOS will not be distinguishable with each other in terms of speed.