Patent ID: 8796057

Claim:
A method of forming a pixel sensor cell, comprising: forming a deep trench isolation structure in a substrate; forming a buried deep trench isolation structure in the substrate; forming a channel region over the buried deep trench isolation structure; forming a photosensitive region within a perimeter formed by the deep trench isolation structure and the buried deep trench isolation structure; and forming gates outside the perimeter, wherein: the deep trench isolation structure and the buried deep trench isolation structure form a diffusion shield surrounding an entire perimeter of a photodiode that includes the photosensitive region; the forming the deep trench isolation structure comprises: etching into the substrate to form a trench of the deep trench isolation structure; lining the trench of the deep trench isolation structure with an insulator; and filling the trench of the deep trench isolation structure with a conductive material; the forming of the buried deep trench isolation structure comprises: etching into the substrate to form a trench of the buried deep trench isolation structure; lining the trench of the buried deep trench isolation structure with the insulator; filling the trench of the buried deep trench isolation structure with the conductive material; forming a recess in the trench of the buried deep trench isolation structure by etching the conductive material in the trench of the buried deep trench isolation structure; removing the insulator in the recess; and capping exposed portions of the conductive material with a capping mask; the capping the exposed portions of the conductive material comprises forming a capping layer in the recess and directly on the exposed portions of the conductive material; and the forming the channel region over the buried deep trench isolation structure comprises forming a silicon material in the recess and directly on the capping layer.