FABRICATION METHOD OF SEMICONDUCTOR OPTICAL WAVEGUIDE ELEMENT, AND SEMICONDUCTOR OPTICAL WAVEGUIDE ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide a fabrication method of a semiconductor optical waveguide element having a semiconductor laminate including a plurality of core layers arranged in a longitudinal direction.SOLUTION: After a waveguide mesa including an upper clad layer 29d and a first core layer 29c is formed, a dummy embedding region embedding the waveguide mesa is formed, and a second mask is formed on the dummy embedding region. The second mask has an opening and a pattern on a first part of the waveguide mesa and has a pattern on a second part of the waveguide mesa. The second mask can be formed on a substantially flat surface of the dummy embedding region and can be patterned with desired fineness. The dummy embedding region can be etched by using the second mask to form a third mask 51 including a dummy embedding mask 41a. The third mask 51 has an opening that reaches to an upper face of the waveguide in the first part of the waveguide mesa where the second mask pattern is transferred.