Abstract: A semiconductor wafer is comprised of a transparent layer interposed between a thin silicon layer and a thick silicon layer. Silicon islands are formed from the thin silicon layer on the transparent layer. Device elements are formed in the silicon islands. Thereafter, the thick silicon layer which is a support layer is etched away to form a transparent region on the wafer. The wafer is constructed to avoid elimination or destruction of the transparent layer during the course of formation of the silicon islands and during the course of etching of the rear thick silicon plate. The transparent layer is comprised of a silicon nitride film or a silicon carbide film. Alternatively, the transparent layer is comprised of a silicon oxide film covered by a silicon nitride film or a silicon carbide film on one or both of the upper and lower faces of the silicon oxide film.