PURPOSE: To improve the state of the contact of a thermally compensating plate and the Al layer of a second main electrode by reducing the thickness of the thermally compensating plate to at least half or more of the thickness of a first electrode while the chamfering of a surface brought into contact with the second main electrode of the thermally compensating plate larger than that of a surface brought into contact with an inserting plate and specifying the surface roughness of the surface brought into contact with the second main electrode of a semiconductor element of the thermally compensating plate and a surface brought into contact with another surface.

CONSTITUTION: A thermally compensating plate 17A is formed in the same thickness as the thickness of a first main electrode 3, both surfaces of the plate 17A are lapping-worked by #1500, only a surface brought into contact with a second main electrode 4 is etched and machined, surface roughness is brought to 0.6-2.0μm, and an outer circumferential section is chamferred by 0.1-0.5mm. The thermally compensating plate 17A and an inserting plate 18 are brought into contact with each other so that the contact interface of the plate 17A and the plate 18 at the time of intermittent conduction can be slid adequately because the surface roughness of a surface brought into contact with the inserting plate 18 of the thermally compensating plate 17A is 0.2-0.5μm, and the sticking of the thermally compensating plate 17A and the Al layer of the second main electrode 4 is prevented because the surface roughness of the surface brought into contact with the second main electrode 4 is 0.6-2.0μm, thus generating no crack in the semiconductor substrate of a semiconductor element 1. The outer circumferential section of the surface brought into contact with the second main electrode 4 of the thermally compensating plate 17A is chamferred by 0.1-0.5mm, thus generating no sag of the Al layer of the second main electrode 4.