US Patent 7894172 ESD protection structure

An ESD protection structure is provided. A substrate includes a first voltage variable material and has a first surface, a second surface substantially paralleled to the first surface and a via connecting the first and second surfaces. A first metal layer is disposed in the substrate for coupling to a ground terminal. The first voltage variable material is in a conductive state when an ESD event occurs, such that the via is electrically connected with the first metal layer to form a discharge path, and the first voltage variable material is in an isolation state when the ESD event is absent, such that the via is electrically isolated from the first metal layer.