Provided is a semiconductor device including a semiconductor substrate provided with a transistor portion, wherein the semiconductor substrate includes, in the transistor portion, a drift region of a first conductivity type; an accumulation region of the first conductivity type that has a higher doping concentration than the drift region; a collector region of a second conductivity type; and a plurality of gate trench portions and a plurality of dummy trench portions that are provided extending in a predetermined extension direction in the top surface of the semiconductor substrate, and are arranged in an arrangement direction orthogonal to the extension direction, and the transistor portion includes a first region that includes a gate trench portion; and a second region in which the number of dummy trench portions arranged in a unit length in the arrangement direction is greater than in the first region.