Semiconductor device including lateral mos element

Abstract

Disclosed is a semiconductor device including a lateral MOS element which comprises a p-type silicon substrate; a first semiconductor layer of an n-type constituting a drift region; a second semiconductor layer of the p-type selectively provided in the first semiconductor layer, and constituting a body region, in which a channel region is partially formed; a third semiconductor layer of the n-type selectively provided in a surface of the second semiconductor layer, and constituting a source region; a fourth semiconductor layer of the n-type provided in the first semiconductor layer, and constituting a drain region; and a trench gate. The trench gate is constructed such that a trench formed in the first semiconductor layer is filled with a gate electrode with an insulating film interposed therebetween. The trench gate is formed such that at least a bottom thereof is in contact with the semiconductor substrate. The semiconductor device of the present invention prevents a high electric field at a corner of the bottom of the trench gate, thus achieving its high breakdown voltage.