A method for manufacturing an laser diode includes: providing a wafer having thereon a semiconductor structure; depositing an SiO.sub.2 film; forming channels and a waveguide ridge between the channels in the wafer; forming an SiO.sub.2 film over the wafer; forming a resist pattern covering the SiO.sub.2 film in the channels such that the top surfaces of the resist pattern are lower than the top surface of the deposited SiO.sub.2 film on the top of the waveguide ridge, the resist pattern exposing the SiO.sub.2 film on the top of the waveguide ridge; removing the SiO.sub.2 film and the deposited SiO.sub.2 film by wet etching, using the resist pattern as a mask, to expose a p-GaN layer in the waveguide ridge; and forming an electrode layer on the top surface of the p-GaN layer.