To provide a bipolar semiconductor device having a low-concentration region in which preferable specific resistance value distribution is formed as a result of the formation of a crystal defect.

An IGBT10 has a p type collector region 14, an n+ type emitter region 24, an n- type drift region 18, and the like. A hole is supplied to the n- type drift region 18 from the p type collector region 14 when the IGBT10 is turned on and the n+ type emitter region 24 and an electron is supplied thereto when it is turned off, so that a conductivity modulation phenomenon is generated in the n- type drift region 18. In the n- type drift region 18, the crystal defect is formed with nearly uniform density. As a result, the n- type drift region 18 has a nearly constant specific resistance value distribution higher than that before crystal defect formation.