Patent ID: 9406794
Filing Date: 2016-08-02
CPC Classification: H01L

Claim Text:
1. A semiconductor device comprising: a semiconductor layer; a first conductivity type region of a first conductivity type formed on a base layer portion of the semiconductor layer; a body region of a second conductivity type formed on the semiconductor layer to be in contact with the first conductivity type region; a trench formed on the semiconductor layer to penetrate through the body region so that a deepest portion thereof reaches the first conductivity type region; a source region of the first conductivity type formed on a surface layer portion of the semiconductor layer around the trench to be in contact with the body region; a gate insulating film formed on a bottom surface and a side surface of the trench; and a gate electrode embedded in the trench through the gate insulating film, wherein the gate insulating film includes a thick-film portion having a relatively large thickness on a peripheral edge portion of the bottom surface of the trench, and a thin-film portion having a relatively small thickness on a central portion surrounded by the peripheral edge portion, a portion of the gate insulating film that is in contact with the side surface of the trench has an upper portion arranged above the thick-film portion, the upper portion having a thickness equal to the thickness of the thin-film portion and less than the thickness of the thick-film portion, the thicknesses of the thick-film portion and the thicknesses of the thin-film portion each being defined by a distance that is measured in a first direction perpendicular to the bottom surface of the trench, and that is between the bottom surface of the trench and a surface of the gate electrode that is in contact with the gate insulating film at a point of the measurement in the first direction, the thickness of the upper portion being defined by a distance that is measured in a second direction perpendicular to the side surface of the trench, and that is between the side surface of the trench and a surface of the gate electrode that is in contact with the gate insulating film at a point of the measurement in the second direction, and the gate insulating film further includes a first portion in direct contact with the source region and a second portion in contact with the body region on the side surface of the trench, the first portion projecting both inwardly and outwardly relative to the trench with respect to the second portion to have a thickness thereof larger than a thickness of the second portion.