Semiconductor structure and method of manufacturing the same

A method of manufacturing a semiconductor structure, comprising:

• forming a trench in a substrate;
• forming a dielectric layer over a first surface of the substrate and on a sidewall of the trench, wherein the dielectric layer extends to a first depth from the first surface of the substrate;
• reducing the first depth of the dielectric layer to a second depth from the first surface of the substrate, and reducing a thickness of the dielectric layer concurrently with the reduction of the first depth to the second depth of the dielectric layer, wherein the second depth is less than the first depth, and the first depth and the second depth are measured from the first surface of the substrate toward a bottom of the trench along a vertical direction;
• and
• forming a diffusion region in the substrate at the sidewall of the trench, wherein the diffusion region extends from the second depth from the first surface of the substrate toward inside the substrate to wrap around the sidewall of the trench and a bottom of the trench.

A semiconductor structure, comprising:

• a semiconductor substrate, including a first surface;
• an deep trench isolation (DTI), disposed in the semiconductor substrate extending from the first surface and stopped inside the semiconductor substrate, wherein the DTI includes a first filling material and a second filling material disposed below the first filling material and separated from the first surface, and the first filling material is different from the second filling material;
• and
• a doping region, disposed in the substrate and surrounding a sidewall and a bottom surface of the second filling material of the DTI, wherein the doping region is separated from the first surface by a doping free region of the semiconductor substrate,
• wherein a bottom surface of the first filling material is in contact with a top surface of the second filling material, and a top portion of the doped region immediately abuts the bottom surface of the first filling material.