High speed junction field effect transistor for use in bipolar integrated circuits

摘要

A high speed BIFET junction field effect transistor is formed in an epitaxial layer (10) of one conductivity type and includes source (18) and drain (20) regions of opposite conductivity type interconnected by a channel region (24) of the opposite conductivity type. A surface layer (26) of the one conductivity type is formed over the channel region, and a highly conductive contact (32) is formed on the surface layer intermediate the source and drain regions. The surface layer can include a region (30) beneath the contact of high dopant concentration of the one conductivity type. The surface contact (32) can comprise highly doped polycrystalline silicon material with or without a metal layer on the surface thereof. Alternatively, the surface contact (32) can comprise a barrier metal contacting the surface layer and a second metal overlying the barrier metal. The surface contact and the epitaxial layer underlying the channel region comprises gates for the field effect transistor. Increased speed of operation comes from the increased conductivity of the surface contact and the limited size and thus reduced capacitance of the surface contact.