PURPOSE: To reduce a thermal resistance and realize a high output power by protrudingly providing a fitting plate which supports a pellet in a package from the circumference of backage as a wide heat radiating plate and by bending to the lower part so that it is in contact with a printed circuit board at the time of loading.

CONSTITUTION: In a semiconductor device 5, a pellet 6 and an internal end of lead 2 are covered with a package 1, a tab 7 loading the pellet 6 is protruded from the circumference of package 1 as a wide plate and is also bent downward, thus forming a surface mounting type heat radiating plate 8. At the time of mounting, a package is placed on a printed circuit board 10 having a wiring layer 9, and the lead 2 and the heat radiating plate 8 are secured by the fused solder 11 which is already printed to the wiring layer 9. Thereby, the generated heat is dissipated into the atmosphere from the wide surface of said wiring surface 9.