Semiconductor laser device and method of fabricating the same

A method of fabricating a semiconductor laser device, comprising:

• forming a mask layer on a substrate;
• patterning the mask layer to form a mask pattern having an opening exposing the substrate;
• forming a single-crystalline germanium layer used as a Fabry Perot cavity in the opening by a selective epitaxial growth (SEG) method;
• and
• forming an electrode on the single-crystalline germanium layer,
• wherein patterning the mask layer includes:
• after etching the mask layer by one of a dry etching process and a wet etching process, etching the mask layer by the other of the dry etching process and the wet etching layer for improving a surface roughness of sidewalls of the mask pattern.