Semiconductor device

A semiconductor device includes: a channel-forming region of a first conductivity type; a first main electrode region of a second conductivity type disposed in a portion of an upper part of the channel-forming region; a drift region 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 of the second conductivity type that is disposed in a part of an upper part of the drift region; and a stopper region 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 developing at the boundary of the pn junction between the channel-forming region and the drift region.