A semiconductor device includes: a wiring substrate; a semiconductor chip mounted on the wiring substrate; a heat release sheet arranged on the semiconductor chip to cover the entire semiconductor chip and having a larger area than an area of the semiconductor chip; and a cover member which covers the semiconductor chip and the heat release sheet and to which the heat release sheet is fixed. The cover member has a first portion facing the semiconductor chip, a flange portion arranged in a periphery of the first portion and bonded and fixed onto the wiring substrate, and a second portion arranged between the first portion and the flange portion. In a plan view of the cover member viewed from the heat release sheet, the heat release sheet is bonded/fixed to the cover member through a bonding member partially arranged between the heat release sheet and the cover member.