A semiconductor device that includes: a semiconductor layer of a first conductivity type, having a peripheral area and a cell area inside of the peripheral area; a region of a second conductivity type in the semiconductor layer in the cell area; and a plurality of guard rings of the second conductivity type in the semiconductor layer in the peripheral area, each having a substantially same depth as the region of the second conductivity type in the cell area. The plurality of guard rings include at least one first ring that has a diffusion region in the depth profile in the semiconductor layer that is wider at a top thereof.