Method and structure providing optical isolation of a waveguide on a silicon-on-insulator substrate

A method of forming an integrated structure, the method comprising:

• forming a shallow trench isolation region in a first semiconductor substrate;
• filing a trench of the shallow trench isolation region with a first dielectric material having a first index of refraction;
• forming a waveguide on a second substrate, wherein the second substrate includes a second dielectric material, wherein the waveguide is formed of a semiconductor material over the second dielectric material, and wherein the semiconductor material has a second index of refraction greater than the first index of refraction;
• and
• attaching the second substrate to the first semiconductor substrate, wherein the second dielectric material faces the first substrate and wherein the waveguide is located over the shallow trench isolation region,
• wherein the shallow trench isolation region comprises silicon dioxide within the trench.