To improve heat-radiation efficiency for application to a semiconductor of high-power chip, by bonding a heat slag on upper and lower surface of a semiconductor chip through a bonding member excellent in heat conductivity, etc.

A second heat slag 7 is provided vertically on both side edges of a plate-like first heat slag 6, and on the upper surface of the first heat slag 6, a semiconductor chip 1 is bonded with the first bonding member 3 of high thermal conductivity. A third heat slag 8 is bonded with the second bonding member 3a of high heat conductivity at the upper-surface center part of the semiconductor chip 1, and on both sides of upper surface of the semiconductor chip 1, plural internal leads 2b where a bottom lead 2a is bent upward are bonded. The internal lead 2b and the chip pad of the semiconductor chip 1 are connected with a lead wire 4, and the inside space of the first third heat slags 6-8 are filled with resin to seal up the semiconductor chip 1, etc., so that a mold part 5 where the bottom lead 2a is exposed is formed.