According to one embodiment, a semiconductor device includes a substrate, a gate electrode, source/drain regions, and a gate insulating film. The substrate is made of monocrystalline silicon, an upper surface of the substrate is a (100) plane, and a trench is made in the upper surface. The gate electrode is provided in at least an interior of the trench. The source/drain regions are formed in regions of the substrate having the trench interposed. The gate insulating film is provided between the substrate and the gate electrode. The trench includes a bottom surface made of a (100) plane, a pair of oblique surfaces made of (111) planes contacting the bottom surface, and a pair of side surfaces made of (110) planes contacting the oblique surfaces. The source/drain regions are in contact with the side and oblique surfaces and are apart from a central portion of the bottom surface.