Patent ID: 9117897
Filing Date: 2015-08-25
Classification: H01L

Abstract:
1. A semiconductor device comprising: a silicon substrate; a first trench formed in a first region of the silicon substrate; a first buried oxide film for burying the first trench; a second trench formed in a second region of the silicon substrate; a second buried oxide film for burying the second trench; a first gate oxide film situated adjacent to the first trench and formed to the surface of the silicon substrate in the first region; a second gate oxide film situated adjacent to the second trench and formed to the surface of the silicon substrate in the second region; a first gate electrode formed over the first gate oxide film; and a second gate electrode formed over the second gate oxide film, wherein the thickness of the second gate oxide film is less than the thickness of the first gate oxide film, wherein the first trench includes: a first tapered portion extended from the surface of the silicon substrate and having a taper; and a first trench main portion extended from the bottom of the first tapered portion and having a taper steeper than the first tapered portion, wherein the second trench includes: a second tapered portion extended from the surface of the silicon substrate and having a taper; a second trench main portion extended from the bottom of the second tapered portion and having a taper steeper than the second tapered portion, wherein a second depth from an upper end of the second trench to a position where the second tapered portion and the second trench main portion are in contact with each other is shallower than a first depth from an upper end of the first trench to a position where the first tapered portion and the first trench main portion are in contact to each other.