Patent ID: 6426236
Filing Date: 2002-07-30
Classification: G02F

Abstract:
A method for making a semiconductor optical modulator, comprising the steps of:forming a first semiconductor buffer layer on a semiconductor substrate; forming a first dielectric mask for selective growth on said first semiconductor buffer layer, said first dielectric mask including two regions in which a dielectric mask width is partially varied and a blank region sandwiched by said two regions; forming a first semiconductor cladding layer, a semiconductor optical absorption layer and a second semiconductor cladding layer in order on said blank region; forming a second dielectric mask for selective growth which has a blank region broader than said blank region of said first dielectric mask; forming a third semiconductor cladding layer and a semiconductor capping layer in order on said blank region of said second dielectric mask for selective growth; forming a first dielectric protective film over the entire top surface of said substrate; forming a second dielectric protective film on said first dielectric protective film; removing said first dielectric protective film and said second dielectric protective film until said semiconductor capping layer is exposed; forming an electrode for applying an electric field to said semiconductor optical absorption layer on said semiconductor capping layer; and removing said second dielectric protective film except under said electrode; wherein said electrode on said semiconductor capping layer is formed all over said semiconductor optical absorption layer, so that a voltage corresponding to an external signal is uniformly applied to said semiconductor optical absorption layer.