A pn junction type solar cell is formed in a predetermined region on a substrate made of glass. Light emitted from a light emitting unit reaches an n-type semiconductor layer after it passed through substrate. The solar cell generates electromotive force corresponding to a quantity of the emitted light. A control circuit, a mask ROM, a transmitting circuit and an antenna are formed on an upper side of the solar cell. A surface of a semiconductor storage device is entirely covered with an insulating film to block entry of outside air. The insulating film is typically formed of physicochemically stable glass or silicon dioxide.