US Patent 11327228 Photonic device and fabrication method thereof

A method for fabricating a photonic device is provided. The method includes forming an optical coupler and a waveguide structure connected to the optical coupler over a semiconductor substrate; forming a metal-dielectric stack over the optical coupler and the waveguide structure; etching a hole in the metal-dielectric stack and vertically overlapping the optical coupler; and forming a protection layer on a sidewall and a bottom of the hole.