Patent attributes
A method of manufacturing a semiconductor device includes the following processes. A first gate trench is formed if a semiconductor substrate region. Then a first insulating film is formed to cover bottom and side surfaces of the first gate trench. Then, the first insulating film is removed to cover the bottom surface. Then, the semiconductor substrate region exposed to the first gate trench is etched by the first insulating film covering the side surfaces as a mask, to form, in the semiconductor substrate region, a second gate trench directly below the first gate trench. The second gate trench is defined by an unetched film portion of the semiconductor substrate region. The unetched film portion extends toward one of the side surfaces of the first gate trench.
