A MOS type semiconductor device wherein on voltage is low, the rate of rise of current at turn-on time is low, and it is possible to hold down the rate of rise of collector current at turn-on time, and reduce radiation noise. The device includes a stripe-shaped plan-view pattern of protruding semiconductor region on an n-type substrate and having a p-type region sandwiched between an upper side n-type first region and a lower side n-type second region, a top flat portion including a depression region with a depth reaching the p-type region, and an inclined portion between the top flat portion and a bottom flat portion around the protruding semiconductor region; and a gate electrode with one end portion of the gate electrode on a surface within the inclined portion, and another end portion on a surface of the lower side n-type second region in the p-type region side vicinity.