Short channel fermi-threshold field effect transistors

Abstract

A Fermi-threshold field effect transistor includes spaced-apart source and drain regions which extend beyond the Fermi-tub in the depth direction and which may also extend beyond the Fermi-tub in the lateral direction. In order to compensate for the junction with the substrate, the doping density of the substrate region is raised to counteract the shared charge. Furthermore, the proximity of the source and drain regions leads to a potential leakage due to the drain field which can be compensated for by reducing the maximum tub depth compared to a low capacitance Fermi-FET and a contoured-tub Fermi-FET while still satisfying the Fermi-FET criteria. The tub depth is maintained below a maximum tub depth. Short channel effects may also be reduced by providing source and drain extension regions in the substrate, adjacent the source and drain regions and extending towards the channel regions. The source and drain extension regions are doped the same conductivity type and doping concentration as the source and drain themselves. A Fermi-FET which is particularly suitable for small linewidths is thereby provided.