Patent ID: 7910987
Filing Date: 2011-03-22
Classification: H01L

Abstract:
1. An insulated gate bipolar transistor, comprising: a semiconductor substrate having a major surface; first and second trenches each having an opening on said major surface and a bottom portion in said semiconductor substrate respectively; first and second impurity regions of the same conductivity type being provided in said semiconductor substrate, the first impurity region being provided to completely surround said bottom portion and partially surround side regions of each of the first and second trenches, the side regions of each of the first and second trenches being continuous to said bottom portion and being in direct contact with the bottom portion and the side regions of each of the first and second trenches, and the second impurity region being provided to be around said opening; a third impurity region arranged to separate the first and the second impurity regions, having a conductivity type that is different from the conductivity type of the first and second impurity regions and being in contact with the side regions of the first and second trenches; an insulating film being directly provided on an inner wall of each of said first and second trenches, a portion of said major surface around said opening, the second impurity region, and on top of an upper side of the substrate between the first and second trenches; and a single polycrystalline silicon film provided oppositely to said semiconductor substrate through said insulating film as a contiguous structure, the single polycrystalline silicon film arranged to fill an inside of both the first and second trenches, to cover the first trench and the second trench and also to cover an upper side of the substrate between the first and second trenches and to extend from one end to the other end over the entire length of the substrate, wherein the thickness of said insulating film along a direction being perpendicular to the thickness direction of said semiconductor substrate in a portion within the trench on two sides of said opening is at least 1.3 times the thickness of said insulating film along said direction on a position being in contact with said semiconductor substrate, and wherein a cross-section of the bottom portion of the first and second trenches is semi-circular.