[Problem] To provide a semiconductor device wherein withstand voltage of a gate insulating film at the upper edge of a trench is improved, and a method for manufacturing the semiconductor device.[Solution] A semiconductor device (1) includes: an n-type SiC substrate (2) having a gate trench (9) formed therein; a gate insulating film (16), which integrally includes a side-surface insulating film (18) and a bottom-surface insulating film (19); and a gate electrode (15) which is embedded in the gate trench (9), and which selectively has an overlap portion (17) that overlaps, at the upper edge (26), the surface (21) of the SiC substrate (2). In the side-surface insulating film (18), an overhung portion (27) that is selectively thick compared with other portions of the side-surface insulating film (18) is formed such that the overhung portion protrudes, at the upper end edge (26), toward the inside of the gate trench (9).