Semiconductor optical device

A ridge waveguide semiconductor optical device, comprising:

• a semiconductor substrate having a front surface and a back surface;
• a lower cladding layer disposed on said front surface of said semiconductor substrate and which comprises a stripe-shaped convex portion;
• an active layer disposed on said convex portion of said lower cladding layer;
• a current blocking layer burying both sides of said convex portion of said lower cladding layer and having a top surface approximately co-planar with a the top surface of said active layer;
• an upper cladding layer disposed on said active layer and said current blocking layer;
• a waveguide area disposed between paired mesa trenches which extend from a surface of said upper cladding layer to said semiconductor substrate, which are approximately parallel to each other and which sandwich said convex portion of said lower cladding layer;
• a first mount area and a second mount area disposed outside said paired mesa trenches;
• a first spacer layer disposed on said upper cladding layer in said first mount area and a second spacer layer disposed on said upper cladding layer in said second mount area;
• a first metal layer electrically connected to said upper cladding layer in said waveguide area and extending from above said waveguide area to over said first mount area;
• and
• a second metal layer disposed over said second mount area, wherein height from the back surface of said semiconductor substrate to a top edge of said first metal layer in said first mount area and height from the back surface of said semiconductor substrate to a top edge of said second metal layer in said second mount area are both larger than height from the back surface of said semiconductor substrate to a top edge of said first metal layer in said waveguide area.