PURPOSE: To thinly form the title semiconductor device without impairing reliability when a high density mounting operation is conducted.

CONSTITUTION: The inner lead part 12a of each lead of a lead frame 12 is connected to each electrode pad 13 on a semiconductor chip 13. An insulating sealing material 14, having the melting point almost same as the melting point of the solder 16, is attached to the upper part of the inner lead part 12a. On the other hand, the outer lead part 12b of each lead is tacked to each substrate wiring 11a on a mounting substrate 11 using solder 16. Then, by adding heat required for mounting, the junction of the outer lead part 12b and the substrate wiring 11a and the sealing of the semiconductor chip 13 are conducted simultaneously using the solder 16 for the former and the fused insulating material 14 for the latter.