A process of forming separation grooves for separating a semiconductor wafer into individual light-emitting devices, a process for thinning the substrate, process for adhering the wafer to the adhesive sheet to expose a substrate surface on the reverse or backside of the wafer, a scribing process for forming split lines in the substrate for dividing the wafer into light-emitting devices, and a process of forming a mirror structure comprising a light transmission layer, a reflective layer, and a corrosion-resistant layer, which are laminated in sequence using sputtering or deposition processes. Because the light transmission layer is laminated on the adhesive sheet, gases normally volatilized from the adhesion materials are sealed and do not chemically combine with the metal being deposited as the reflective layer. As a result, reflectivity of the reflective layer can be maintained.