SEMICONDUCTOR DEVICE AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a semiconductor device having a sufficient reverse bias safe action region. SOLUTION: An n-substrate 11 has a first main face having an outer circumferential face P1oand an inner circumferential face P1i surrounded by the outer circumferential face P1o, and a second main face opposed to the first main face. An insulation gate type field transistor part FT is provided on the inner circumferential face P1i of the n-substrate 11. An n+ layer 15 is provided on the part opposed to the circumferential face P1oof the second main face, and has an impurity concentration higher than that of the n-substrate 11. An n++ buffer layer 20 of which at least a part is located on the part opposed to the circumferential face P1oof the second main face, and has an impurity concentration higher than that of the n+ layer 15. A p+ layer 16 is provided on the n+ layer 15 and the n++ buffer layer 20. COPYRIGHT: (C)2009,JPO&INPIT