PURPOSE: To effectively radiate the heat generated by a semiconductor element to external side even in a circuit substrate in the TAB mounting.

CONSTITUTION: Semiconductor elements 11 which generate heat are mounted on the upper surface of a multilayer circuit substrate 10 by the TAB mounting method and moreover a heat radiating fin 12 is provided at the bottom layer of the multilayer circuit substrate 10. The semiconductor elements 11 are electrically connected with the multilayer circuit substrate 10 via a lead terminal 13 by the TAB mounting method. In the multilayer circuit substrate 10, through holes 14 are bored at the area between the semiconductor element 11 and heat radiating fin 12 and column members 15 which are almost in the same shape as the through holes are engaged with such through holes 14. This column member 15 is integrally provided at the rear surface side of the heat radiating fin 12 and paste 16 having a high heat conductivity is provided between the upper surface of the column member 15 and the bottom of the semiconductor element 11.