A method of production of a semiconductor device able to utilize a conventional production system for a resin board to thereby produce a wafer level package without increasing the production cost, comprising electrolessly plating the electrode terminals to cover the surfaces of the electrode terminals by a protective film protecting the electrode terminals from laser beams; grinding the back side of the semiconductor wafer to reduce the thickness of the semiconductor wafer before or after forming the protective film; covering the entirety of the electrode terminal forming surface and back side of the semiconductor wafer, having the electrode terminals covered by a protective film and processed to reduce the thickness of the semiconductor wafer, by a resin to form a laminate; and focusing a laser beam toward the electrode terminal forming surface of the semiconductor wafer from outside the laminate to form via holes with the protective film exposed at their bottom surfaces, then filling the via holes by electroplating to form the conductor parts.