To provide a semiconductor device that exhibits a high breakdown voltage, excellent thermal properties, a high latch-up withstanding capability and low on-resistance. The semiconductor device according to the invention, which includes a buried insulator region 5 disposed between an n−-type drift layer 3 and a first n-type region 7 above n−-type drift layer 3, facilitates limiting the emitter hole current, preventing latch-up from occurring, raising neither on-resistance nor on-voltage. The semiconductor device according to the invention, which includes a p-type region 4 disposed between the buried insulator region 5 and n−-type drift layer 3, facilitates depleting n−-type drift layer 3 in the OFF-state of the device. The semiconductor device according to the invention, which includes a second n-type region 6 disposed between the first n-type region 7 and the n−-type drift layer 3, facilitates dissipating the heat caused in the channel region or in the first n-type region 7 to a p+-type collector layer 1a, which is a semiconductor substrate, via the second n-type region 6, n−-type drift layer 3 and an n-type buffer layer 2.