BiCMOS device having self-aligned well tap and method of fabrication

摘要

A well tap for a field effect device formed using a single polysilicon process and a silicide layer is provided. The polysilicon layer which makes contact to the well is doped the same way as the well but is doped opposite of the source or drain. The silicide layer is formed on the upper and sidewall surfaces of the source or drain, well tap, and gate contacts for a field effect device. The silicide layer extends from the sidewall silicide across the upper surface of the transistors and up to the sidewall oxide of the transistor gates. The structure makes it possible to eliminate laterally-spaced separate well taps used in previous devices. Elimination of the laterally-spaced well taps permits higher packing density, and lowers buried layer-to-substrate capacitance.