Patent ID: 7879635

Claim:
A method for manufacturing a semiconductor optical device comprising: forming a laminated semiconductor structure including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, in sequence, on a semiconductor substrate; forming, in a photolithography process, a first resist pattern of a first resist film on a top surface of the laminated semiconductor structure, the first resist pattern having a stripe-shaped portion having a width corresponding to a waveguide ridge; removing upper portions of the second semiconductor layer by dry etching, using the first resist pattern as a mask, forming concave portions sandwiching the waveguide ridge, and leaving a lower portion of the second semiconductor layer at the concave portions; removing the first resist pattern; forming a first insulating film on the top surface of the laminated semiconductor structure and in the concave portions; forming a second resist film covering the first insulating film in the concave portions and on the waveguide ridge; patterning the second resist film and forming a second resist pattern exposing the first insulating film on the waveguide ridge and respective portions of bottom surfaces of the concave portions, adjacent the waveguide ridge, the second resist pattern, in the concave portions, having a top surface at each of the concave portions farther from the substrate than a top surface of the second semiconductor layer in the waveguide ridge, and closer to the substrate than a top surface of the first insulating film on the waveguide ridge; heating the second resist film so that at least some of the second resist film in the concave portions flows and entirely covers the bottom surfaces of the concave portions; removing exposed portions of the first insulating film by etching, using the second resist pattern as a mask, and exposing the second semiconductor layer on the waveguide ridge; and forming an electrode layer on the second semiconductor layer on the waveguide ridge.