PURPOSE: To improve the heat dissipating property by composing a lead frame connecting a tab made of a material close to the coefficient of thermal expansion of a pellet and a lead made of a material of a high conductivity.

CONSTITUTION: A tab 11 made of a material such as Kovar 42 and alloy closer to the coefficient of thermal expansion of a semiconductor pellet 20 and a lead 14 made of a material, such as copper, higher in the heat conductivity than the tab 11 are connected solidly to form a lead frame. A semiconductor pellet 20 is fastened on a tab 11 of the lead frame while a wire bonding is made between the pellet 20 and the lead 14 with a wiring. Then, the lead 14, the pellet 20, the wire 21 and the like are packaged.