PURPOSE: To prevent the warping of a package produced by the thermal shrinkage of a resin after the package is formed by sealing a semiconductor chip with the resin when the package is formed to a uniform thickness on the opposite sides of a lead frame on which the semiconductor chip is mounted by mounting a dummy semiconductor chip on the lower surface of the island section of the lead frame.

CONSTITUTION: A dummy semiconductor chip 1 formed of the same material as that used for a semiconductor chip 2 to the same dimension as that of the chip 2 is mounted on the lower surface of the island section 3 of a lead frame, on the upper surface of which the chip 2 is mounted. For example, the chip 2 is mounted on the upper surface of the island section 3 of the lead frame by die bonding with a bonding agent 7 and the chip 2 is electrically connected with external terminals 5 with bonding wires 4. In addition, the dummy chip 1 is mounted on the lower surface of the island section 3 by similar die bonding. Then the chip 2 and 1 are sealed with a sealing resin 6 so that the thickness of the package can have a uniform thickness on the opposite sides of the lead frame.