Patent ID: 7781802

Claim:
A semiconductor device including a semiconductor base of a predetermined conduction type, a hetero semiconductor region being in contact with a first main surface of the semiconductor base and formed of a semiconductor material different in band gap from the semiconductor base, a first electrode connected to the hetero semiconductor region, and a second electrode connected to the semiconductor base, wherein the hetero semiconductor region is composed of a first hetero semiconductor region of a same conduction type as the conduction type of the semiconductor base and a second hetero semiconductor region of a conduction type different from the conduction type of the semiconductor base, both of the first hetero semiconductor region and the second hetero semiconductor region are ohmically connected to the first electrode and form a heterojunction to the semiconductor base, the first hetero semiconductor region is formed on the first main surface of the semiconductor base, the first hetero semiconductor region forms a first heterojunction interface at the first main surface, and the second hetero semiconductor region is formed in trenches dug on the first main surface of the semiconductor base so as to form a second heterojunction interface to be deeper in the semiconductor base toward the second electrode than the first heterojunction interface.