PURPOSE: To obtain an inexpensive case characterized by high lead position accuracy and excellent mass productivity, by welding a plurality of lead frames to the glass part of an insulating substrate, which has a glass layer on the surface of the outer part of a recessed part, on which a semiconductor element is fixed.

CONSTITUTION: A lead frame 3 is formed out of a belt shaped thin metal plate comprising a copper alloy, on which an Al film is applied, by a press. At this time, Al film parts are positioned at the tips of leads 4. At the center of a ceramic substrate 9, a recessed part 8 which fixes a semiconductor element is provided. On the surface of the peripheral part of the ceramic substrate 9, a low melting point glass 7 is applied. The ceramic substrate 9 is mounted on a supporting table having guide pins. The two lead frames 3 and 3' are mounted on the ceramic substrate 9 so that the Al parts 5 face upward. The guide pins are inserted into guide pin holes 6 and fixed. Then the device is heated to 400W 500°C, and the lead frames 3 and 3' and the ceramic substrate 9 are welded to each other.