Method of manufacturing semiconductor optical element

A method of manufacturing a semiconductor optical element, comprising:

• successively stacking a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type;
• applying a resist on the second semiconductor layer and patterning the resist into stripes by photolithography;
• forming recesses with the second semiconductor layer at the bottom of the recesses and a waveguide ridge adjacent to the recesses, by dry-etching the second semiconductor layer to a depth only partially through the second semiconductor layer, using the resist as a mask;
• forming an insulating film on the waveguide ridge and in the recesses without removing the resist;
• removing the insulating film on the resist by etching, utilizing a difference in etching rate between the insulating film on the resist and the insulating film in the recesses so that the resist is exposed and the insulating film in the recess is left;
• removing the resist that is exposed;
• and
• forming an electrode on the waveguide ridge after removing the resist.