Integrated optical device and fabrication method thereof

A fabrication method for an integrated optical device having a first semiconductor optical element that is provided on a first region of a main face of a substrate and a second semiconductor optical element that is provided on a second region of the main face of the substrate and that is optically coupled to the first semiconductor optical element, comprising the steps of:

• forming a first III-V compound semiconductor layer containing an Al element on the main face of the substrate;
• forming a second III-V compound semiconductor layer for forming the first semiconductor optical element on the first III-V compound semiconductor layer;
• forming an etching mask on the first region after forming the second III-V compound semiconductor layer;
• forming the first semiconductor optical element by using the etching mask to dry-etch the second III-V compound semiconductor layer;
• and
• forming the second semiconductor optical element on the second region after forming the first semiconductor optical element,
• wherein, in the step of forming the first semiconductor optical element, an end point of dry etching is detected by performing dry etching while detecting the Al element.