A semiconductor device includes a circuit pattern over a first surface of a substrate, an insulating interlayer covering the circuit pattern, a TSV structure filling a via hole through the insulating interlayer and the substrate, an insulation layer structure on an inner wall of the via hole and on a top surface of the insulating interlayer, a buffer layer on the TSV structure and the insulation layer structure, a conductive structure through the insulation layer structure and a portion of the insulating interlayer to be electrically connected to the circuit pattern, a contact pad onto a bottom of the TSV structure, and a protective layer structure on a second surface the substrate to surround the contact pad.