To provide a semiconductor device in which dielectric breakdown strength in a peripheral region is increased without increasing on-resistance. An IGBT comprises a body region, guard ring, and collector layer. The body region is formed within an active region in a surface layer of a drift layer. The guard ring is formed within a peripheral region in the surface layer of the drift layer, and surrounds the body region. The collector layer is formed at a back surface side of the drift layer, and is formed across the active region and the peripheral region. A distance F between a back surface of the guard ring and the back surface of the drift layer is greater than a distance between a back surface of the body region and the back surface of the drift layer. A thickness H of the collector layer in the peripheral region is smaller than a thickness D of the collector layer in the active region.