Photonic waveguide and method of forming the same

A semiconductor device, comprising:

• a photonic waveguide for transmitting light in a substrate, the photonic waveguide comprising:
• a first section formed of a first material and arranged in a first layer of the photonic waveguide;
• and
• a second section formed of a second material different from the first material and arranged in a second layer of the photonic waveguide, wherein one of the first section and the second section comprises a plurality of periodic structures overlapping the other from a top-view perspective,
• wherein the first material is silicon, and the second material is silicon nitride.

A semiconductor device, comprising:

• a first substrate comprising a first dielectric layer;
• a second substrate bonded to the first substrate;
• and
• a photonic waveguide arranged in the first substrate and the second substrate, wherein the photonic waveguide comprises:
• a first section extending in a first direction in the first substrate and having a first refractive index, wherein the first section comprises a plurality of periodic structures, and the first dielectric layer wraps around the first section;
• and
• a second section extending in a second direction in the second substrate and having a second refractive index different from the first refractive index, wherein the second direction is different from the first direction, and the second section overlaps with the plurality of periodic structures of the first section from a top-view perspective,
• wherein the first dielectric layer has a third refractive index less than the first refractive index, and the second substrate comprises a second dielectric layer wrapping around the second section of the photonic waveguide and having a fourth refractive index less than the second refractive index.