One embodiment provides a semiconductor device having: a core substrate having first and second surfaces and an accommodation hole penetrating therethrough; a semiconductor element accommodated in the accommodation hole so that a front surface thereof is on the first surface side; a first metal film formed on a back surface of the semiconductor element; a second metal film formed on the second surface of the core substrate; an insulating layer covering the first and second metal films; and a third metal film formed on the insulating layer, via parts thereof penetrating through the insulating layer to respectively reach the first and second metal films.