A polysilicon fuse is disclosed that is capable of securing good insulation after being cut into small areas. A manufacturing method for the fuse and a small-size and highly-reliable semiconductor device including a polysilicon fuse also are disclosed. By forming a cavity inside a polysilicon portion serving as a melting portion by setting the melting portion of the polysilicon fuse to be a vertical type, a gap is formed between an upper part electrode and the surface of melted polysilicon when the polysilicon fuse is cut off. Because of this gap, good insulation can be secured. By using this polysilicon fuse, a semiconductor device that has a small size and high reliability is provided.