The present invention relates to a semiconductor device, the purpose of which is to protect the transistor of the internal circuit from the influence of ESD surge caused by the cross section of the redundant fuse of the semiconductor device. The semiconductor device is characterized in that the device comprises a semiconductor substrate added with a first conductivity-type impurity; an insulatingfilm formed on the surface of the semiconductor substrate; a fuse formed on the insulating layer; a first diffusion layer added with a second conductivity-type impurity and formed on the surface of the semiconductor substrate, and the first diffusion layer is electrically connected with the fuse; a second diffusion layer electrically connected with the substrate and formed on the surface of the semiconductor substrate, and the second diffusion layer is added with the first conductivity-type impurity, the thickness of which is higher than the first conductivity-type impurity added to the semiconductor substrate; and the second diffusion layer, the first diffusion layer, and the semiconductor substrate are associated to form a diode; and a transistor electrically connected with the first diffusion layer.