etching an active layer and clad that are stacked on a semiconductor substrate in sequence into a first alignment key, a second alignment key and an optical area, said etching being determined by patterns in said clad, some of said patterns being deemed as alignment patterns;

removing said alignment patterns after said etching is completed;

growing at least two insulating layers at the etched portions between the first and second alignment keys and the optical areas;

forming protection masks on the first and second alignment keys, said protection masks covering said alignment keys and extending onto select portions of said at least two insulating layers;

forming an electrode on the optical area and the insulating layers; and

removing said protection masks after said electrode is formed.