PURPOSE: To obtain a semiconductor device which is strong enough to withstand large consumption of electricity by making the face down bonding plane of a semiconductor chip with which a heat sink is in a close contact is bonded to a wiring substrate plane.
CONSTITUTION: A collet 1 transfers a semiconductor chip 2 to right above a heat sink 3 by attracting the face down bonding plane of the semiconductor chip 2 and puts it on the heat sink 3 by determining its position. The chip 2 and the heat sink 3 are welded by heating them at the prescribed temperature. The collet 1(1') attracts the opposite plane of the heat sink 3 with which the chip 2 is in a close contact and transfers it after determining its position to the prescribed one on an interconnection substrate 4. The collet 1(1') makes the face down bonding plane of the chip adhere to solder bumps located on the substrate 4. After that, the face down bonding plane of the chip 2 is connected with the substrate 4 through the bumps 5 by heating at a prescribed temperature.