Patent ID: 9620546
Date: 2017-04-11
CPC Classifications: H01L

Claim:
1. A pixel unit comprising: a semiconductor substrate having first and second opposite major surfaces, and a trench extending vertically from the first major surface to delimit an active region of the substrate, internal side surfaces delimiting sides of the trench and a bottom surface delimiting an internal bottom of the trench remote from the first major surface of the semiconductor substrate; a photoelectric conversion element in the active region and that generates charges in response to light incident on the first major surface of the substrate; and a trench isolation structure in the trench, wherein the trench isolation structure comprises a body of a first material occupying a majority of the trench, a second material disposed within the body of the first material, and a third material on the first and second materials, the body of the first material has an inner boundary, the second material has an outer boundary, and a seam between the body of the first material and the second material exists along the outer boundary of the second material and at least part of the inner boundary of the body of the first material, and the inner boundary of the body of the first material extends to the internal bottom surface delimiting the bottom of the trench.