Patent ID: 7456039

Claim:
A method for manufacturing a semiconductor optical device, comprising: forming a dielectric film on a top surface of 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 substrate, the dielectric film having a thickness da and having an etch rate Ra in a predetermined etchant; forming, by photolithography, a first resist pattern of a resist film disposed on a top surface of the dielectric film, the first resist pattern having a stripe shape corresponding to a waveguide ridge; removing part of the dielectric film by etching, using the first resist pattern as a mask, to expose part of the second semiconductor layer; removing portions of the second semiconductor layer by dry etching, using the first resist pattern as a mask, to form the waveguide ridge, the portions of the second semiconductor layer removed formerly extending from a top surface of the second semiconductor layer toward a bottom of the second semiconductor layer; forming a first insulating film on a top and both sides of the waveguide ridge while leaving the first resist pattern in place, the first insulating film having a thickness db and having an etch rate Rb in the predetermined etchant, where 1<(db/Rb)/(da/Ra); removing the first resist pattern and the portion of the first insulating film on top of the waveguide ridge by wet etching; wet etching for a predetermined period of time in the predetermined etchant to remove the dielectric film from the top of the waveguide ridge and to expose the second semiconductor layer, while leaving the first insulating film in place on both sides of the waveguide ridge; and forming an electrode layer on the second semiconductor layer in the waveguide ridge.