Semiconductor device

The invention provides a semiconductor device that ensures a device withstand voltage and achieves downsizing. A semiconductor device includes: a channel-forming region (2) of a first conductivity type; a first main electrode region (10j) of a second conductivity type disposed in a portion of an upper part of the channel-forming region; a drift region (3j) of the second conductivity type that is disposed in an upper part of the channel-forming region apart from the first main electrode region; a second main electrode region (11j) of the second conductivity type that is disposed in a part of an upper part of the drift region; and a stopper region (4j (4aj, 4bj)) of the second conductivity type that is disposed at an end region of the drift region apart from the first main electrode region and has a higher concentration than the drift region. The stopper region restricts extension of a depletion layer (20a) developing at the boundary of the pn junction between the channel-forming region and the drift region.