A semiconductor device comprises: a semiconductor element; a support substrate arranged on a surface of the semiconductor element opposite to a surface thereof provided with a pad, the support substrate being wider in area than the semiconductor element; a burying insulating layer on the support substrate for burying the semiconductor element therein; a fan-out interconnection led out from the pad to an area on the burying insulating layer lying more peripherally outwardly than the semiconductor element; and a reinforcement portion arranged in a preset area on top of outer periphery of the semiconductor element for augmenting the mechanical strength of the burying insulating layer and the fan-out interconnection.