Reversed source-drain mosgated device

摘要

A MOSgated device with a minimum overlap between the gate and drain electrodes is comprised of an N+ substrate which receives an epitaxial layer of silicon. The body of the epitaxial layer has an N- lower layer for an accumulation device or a P- drift lower layer. In each case the top of the epitaxial layer is N+. Both can be operated in an a-c mode. A trench gate consists of a trench through the epitaxial layer which has a thin gate oxide layer on its walls and bottom and a conductive polysilicon gate body filling the trench. The thin oxide on the bottom of the trench may be thicker than the oxide on the walls to reduce gate capacitance. A thick isolation oxide which is about 10 times as thick as the gate oxide overlies the top of the polysilicon. A planar drain electrode overlies the N+ top layer and the laterally spaced isolation oxide; and a planar source electrode contacts the bottom of the substrate.