PURPOSE: To ensure a highly efficient heat dissipation by providing the concavity to the resin-sealed substance to expose the surfaces of the side bonded with the semiconductor pellet of the tab and the opposite side and securing a contact between part of the heat sink and the back of tab.

CONSTITUTION: Semiconductor pellet 11 containing the prescribed pn junction is placed and bonded onto tab 12, and plural units of lead 14 are provided with nearly the same level as tab 12 and at both sides of tab 12 with extension toward the side direction. The tab side of lead piece 14 and pellet 11 are connected together via bonding wire 15, and resin-sealed substance 16 covers over pellet 11, tab 12, the tab side of piece 14 plus wire 15 respectively. Here, the concavity is provided to substance 16 to expose the surfaces of the side bonded with pellet 11 of tab 12 and its opposite side and with connection of heat sink 18. As a result, a contact is secured between part of heat sink 18 and the back of 12, thus ensuring a highly efficient heat dissipation.