It is an object of the present invention to provide a molded semiconductor device which allows its package to be mounted on an external circuit even if the width of the conductor of a high-frequency signal transmission line on a packaging substrate of an external circuit is large, when the molded semiconductor device is to be connected to the external circuit. A semiconductor chip 3 is mounted on a first metal member 2 by mounting solder of AuSn or the like by bonding. The semiconductor chip 3 has a high-frequency signal terminal connected to a second metal member 1 by a metal wire 4 of Au or the like by bonding. The second metal member 1 is branched in a mold area 6 into two central conductors 1a, 1b which extend out of the mold area 6. The first metal member 2 has two ground conductors 2a, 2b which are disposed one on each side of the central conductors 1a, 1b. If an existing semiconductor package has a lead pitch P and a lead width M, then the distance L.sub.2 between the ground conductors 2a, 2b may be determined by (3.times.P-M), and is typically 1.73 mm. Since the distance L.sub.2 is greater than the width B (1.3 mm) of a conductor 10 on a packaging substrate of an external circuit, the central conductors 1a, 1b can be mounted on the conductor 10 on the packaging substrate.