Patent ID: 8729608

Claim:
A semiconductor device, comprising: a substrate having a semiconductor layer on a principal surface thereof; a trench having a bottom, a first side surface and a second side surface opposite to the first side surface, and provided in the semiconductor layer; a gate insulating film covering a top of the semiconductor layer around the trench, and the bottom, the first side surface and the second side surface of the trench; a gate electrode including a portion filling the trench and a portion expanding around the trench, and provided on the gate insulating film; an interlayer insulating film covering a top of the gate electrode; and a hollow provided in a region above and around the trench, and between the gate electrode and the gate insulating film, wherein above the trench, part of the hollow protrudes from a first plane toward a second plane, the first plane extending from a first interface between the gate insulating film on the first side surface of the trench and the gate electrode inside the trench, and the second plane extending from a second interface between the gate insulating film on the second side surface of the trench and the gate electrode inside the trench.