An N+ buffer layer formed on the underside of an N− layer includes an inactive region having incompletely activated ions and an active region having highly activated ions. The carrier concentration of the active region is higher than that of the inactive region. In the inactive region, the electrical activation rate X of the ions is expressed as 1%≦X≦30%. It is thus possible to achieve a PT structure using a Raw wafer, which reduces manufacturing costs and suppresses power consumption.