Patent ID: 6846694

Claim:
A method for producing a semiconductor device with a built-in light receiving element, wherein the device comprises a light receiving element region for receiving and converting an optical signal to an electric signal, the light receiving element region being provided on a substrate, the method comprising: forming an anti-reflection film in the light receiving element region on the substrate; forming a protection film over the anti-reflection film, the protection film serving as an etch stop film for protecting the anti-reflection film in a subsequent etching step; forming at least one additional film over the protection film; etching a light-receiving window in the at least one additional film over the light receiving element region so that said etching removes material down to the protection film wherein the protection film is located at the bottom of the window following said etching, so that the protection film protects the anti-reflection film from being etched during said etching of the light-receiving window; and thereafter removing the protection film completely from the bottom of the window.