Abstract: A semiconductor optical function device includes a semiconductor substrate having a substrate edge surface; an optical waveguide formed on the semiconductor substrate; a non-waveguide region formed on the semiconductor substrate between the optical waveguide and the substrate edge surface; and an insulation region disposed around the optical waveguide and having a semiconductor interface contacting with the non-waveguide region on a side of the substrate edge surface. The semiconductor interface extends not in parallel to the substrate edge surface, and is inclined relative to the substrate edge surface by a specific angle.