PURPOSE: To make adhesion between a lead frame and resin favorably, and to obtain the semiconductor device having superior moisture proofness by a method wherein the lead frame and the resin are formed of materials having nearly the equal coefficients of thermal expansion.

CONSTITUTION: After a semiconductor element 2 is fixed on a tab 3, each electrode of the element 2 and the inside edge of a lead 5 are connected with a wire 9. After then, the element 2 and the inside edge parts of the leads 5 are molded with the resin to form the molded part 10. Then dams 8 are cut to be removed, while outside frames 6 are cut apart from the leads 5, and the group of the leads protruding on both the sides from the molded part 10 are bent in the same direction to form the dual-in-line type semiconductor device 11. The coefficients of thermal expansion of aluminum to form the lead frame and the resin are nearly equal, and when both are heated an cooled up to the normal temperature at molding time, the constricted conditions of both become to be nearly equal with each other.