Provided is a semiconductor device having a superjunction structure formed by a first conduction type column and a second conduction type column, including a first region of the superjunction structure in which a PN ratio increases in a direction from a first surface side to a second surface side of the superjunction structure; and a second region of the superjunction structure that contacts the first region and is adjacent to a channel region of the semiconductor device, wherein a PN ratio of the second region is less than the PN ratio at an end of the first region on the second surface side and thickness of the second region is less than thickness of the first region.