Patent ID: 9299833
Filing Date: 2016-03-29
CPC Classification: H01L

Claim Text:
1. A semiconductor device comprising: an insulating layer; a semiconductor layer of a first conductive type, laminated on the insulating layer; an annular deep trench having a thickness reaching the insulating layer from a top surface of the semiconductor layer, the annular deep trench defining an edge of an element forming region therein; an annular body region of a second conductive type formed across an entire thickness of the semiconductor layer so as to have a thickness reaching the insulating layer from a top surface of the semiconductor layer along a side surface of the annular deep trench in the element forming region; a drain region of the first conductive type formed at an almost center of the element forming region, the drain region formed in the top surface of the semiconductor layer; an annular drift region of the first conductive type formed between the annular body region and the drain region in the element forming region; a source region of the first conductive type formed in a top layer portion of the annular body region; an insulative film formed on the drift region, the insulative film having an opening in which the drain region is exposed; and a first conductive type region formed in the drift region, said first conductive type region expanding under the drain region and having a deepest portion reaching a position deeper than the drain region, and having a first conductive type impurity concentration higher than the first conductive type impurity concentration of the semiconductor layer and lower than the first conductive type impurity concentration of the drain region, wherein the drain region extends over an entire area of the opening, the insulative film includes a middle portion having a constant thickness and an edge portion located between the middle portion and the opening, all of the edge portion has a thickness becoming thinner toward the opening, the drain region is in direct contact with the insulative film, the first conductive type region is formed adjacent to the drain region so that the entirety of the first conductive type region is arranged in a region directly beneath the opening and the edge portion, and vertical edges of the first conductive type region are symmetrically in direct contact with part of the edge portion of the insulative film.