High-frequency performance of submicrometer channel-length silicon MOSFET's

Polycide-gate silicon n-channel MOSFETs were fabricated on the basis of a standard 0.5-micron MOS technology and measured over the 1.5-26.5-GHz frequency range, in order to investigate the effects of channel-length reduction on device behavior at high frequency. Excellent microwave performances were obtained with a maximum operating frequency (fmax) and a unity-current-gain frequency ft near 20 GHz for 0.5-micron-gate-length NMOS devices. An equivalent circuit for a MOSFET with its parasitic elements was extracted from measured S-parameter data. The influence of gate resistance, gate-to-drain overlap capacitance, substrate conductivity, and the transit-time effect between the source and drain on microwave characteristics was analyzed.