Patent ID: 7638409

Claim:
A method for manufacturing a semiconductor device, the method comprising steps of: forming a first layer including impurities on a semiconductor substrate; forming a second layer on the first layer; forming a first trench in the second layer, the first trench including an inner surface having a corner; forming a first thermal oxidation film on the inner surface of the first trench by performing a first thermal oxidation process; forming a first embedment layer in the first trench; forming a second trench in the first trench, the second trench including an inner surface having a corner and being deeper than the first trench; forming a second thermal oxidation film on the inner surface of the second trench by performing a second thermal oxidation process; and forming a second embedment film in the second trench, wherein the step of forming a first thermal oxidation film includes rounding the corner of the first trench, and the step of forming a second thermal oxidation film includes rounding the corner of the second trench and forming the second thermal oxidation film so as to be thinner than the first thermal oxidation film.