Method of making semiconductor optical guided-wave device

A method for producing a semiconductor optical guided-wave device, said method comprising the steps of:

• forming a first semiconductor cladding layer on a surface of a semiconductor substrate, said surface being in the (100)-plane;
• and
• forming a semiconductor guiding layer on said first semiconductor cladding layer;
• forming a second semiconductor cladding layer on said semiconductor guiding layer;
• forming a dielectric mask layer on said second semiconductor cladding layer, said mask having a stripe-shaped gap which extends in the [011]-direction;
• selectively forming a third semiconductor cladding layer on said second semiconductor cladding layer through said stripe-shaped gap by using said dielectric mask layer and a crystal growth technique;
• forming a semiconductor cap layer on said third semiconductor cladding layer;
• said semiconductor cap layer and said third semiconductor cladding layer forming a ridge which extends in the [011]-direction, and said ridge having a substantially trapezoidal cross-section taken in a direction perpendicular to a longitudinal direction of said ridge;
• said ridge having tilted side faces extending parallel to said longitudinal direction of said ridge in said (111)-planes;
• forming an optical waveguide in said semiconductor guiding layer at a position just below said ridge;
• applying dielectric protection layer, after removing said dielectric mask layer, said dielectric protection layer covering an uncovered surface of said second semiconductor cladding layer and an entire surface of said ridge including said tilted side faces;
• forming a window in said dielectric protection layer at a top face of said ridge;
• forming a first electrode through said window, and said first electrode contacting said top face of said semiconductor cap layer;
• and
• forming a second electrode on a back surface of said semiconductor substrate.