A semiconductor device includes a multilayer structure including an n− i layer, a p anode layer formed on the front surface of the n− i layer, an n− buffer layer formed on the back surface of the n− i layer, an n+ cathode layer and a p collector layer formed on the back surface of the n− buffer layer or on the back surfaces of the n− i layer and the n− buffer layer such that the n+ cathode layer and the p collector layer are adjacent to each other in a plan view or adjacent portions thereof overlap each other in a plan view, a front surface electrode, and a back surface electrode. A vertical position in the multilayer structure of the n+ cathode layer in the multilayer structure differs from that of the p collector layer.