In a semiconductor device, a plurality of small depressions are formed to overlap each other in a first joining region of a back surface of a heat releasing plate. A streaky scratch or the like created on the back surface of the heat releasing plate is removed or reduced, by forming the small depressions overlapping each other on the heat releasing plate. In addition, when the small depressions are formed in the first joining region of the back surface of the heat releasing plate, the hardness of the first joining region of the back surface increases. Hence, the scratch is prevented from being created on the back surface of the heat releasing plate on which the depressions are formed to overlap each other in the first joining region of the back surface.