SEMICONDUCTOR DEVICE PROVIDED WITH MIS FIELD-EFFECT TRANSISTOR

摘要

PURPOSE:To provide a semiconductor device provided with a MIS fieldeffect transistor whose breakdown voltage is fixed at a prescribed value and which is restrained from changing in breakdown strength with time and high-in reliability. CONSTITUTION:A second P-type base layer 23 is formed on the main surface of an N-type well layer 111 between a MOS 125 and a drain 126 extending over a first P-type base layer 12 and a N-type base 19. A P-type well-like anode region 130 is provided under a drain contact layer 20 deeper than the N-type base layer 19 and apart from the second base layer 111. The anode region 130 and the N-type base layer 19 are made to serve as a breakdown strength- limiting diode or a sacrifice diode, and when the diode carries out a forward blocking function, a depletion layer is expanded from an interface between the anode region 130 and the N-type base layer 19. and a spot 124 where a breakdown takes place first is located at a junction of the anode region 130 and the N-type base layer 19.