A method for manufacturing a semiconductor device includes: forming sequentially an n− type epitaxial layer and an n+ type area on a first surface of an n+ type silicon carbide substrate; forming a plurality of first trenches and a plurality of second trenches by etching the n− type epitaxial layer and the n+ type area using a first mask pattern as a mask after forming the first mask pattern on the n+ type area; forming a groove by etching the first mask pattern using a first photosensitive film pattern as a mask after forming the first photosensitive film pattern in the plurality of first trenches; forming a p type area by injecting p ions in the plurality of second trenches using the first mask pattern with the groove as the mask after removing the first photosensitive film pattern; forming a gate insulating layer in the plurality of first trenches after removing the first mask pattern with the groove; forming a gate electrode on the gate insulating layer; forming a passivation layer on the gate electrode; forming a source electrode in the plurality of second trenches; and forming a drain electrode on a second surface which is an opposite side to the first surface of the n+ type silicon carbide substrate.