Image sensor illuminated and connected on its back side

A method, comprising:

• manufacturing an image sensor, the manufacturing including:
• forming a stack of dielectric layers on a back side of a semiconductor layer, the semiconductor layer have a front side opposite to the back side;
• simultaneously etching, starting from a front side of the semiconductor layer, first and second trenches through the semiconductor layer and into the stack to first and second depths, respectively, the first depths of the first trenches being deeper into the stack than the second depths of the second trenches;
• forming pixels in the semiconductor layer, the second trenches separating the pixel from each other;
• forming a dielectric liner layer on walls of the first and second trenches;
• filling the first and second trenches with a layer of a first conductive material, wherein filling the first and second trenches includes forming laterally-insulated conductive fingers extending through the semiconductor layer from a front side of the semiconductor layer and forming conductive walls that, together with the dielectric liner layer in second trenches, separate the pixels from each other, the walls extending through the semiconductor layer from the front side and having a lower height than the fingers;
• forming a conductive layer extending along part of a height of the stack and flush with an exposed surface of the stack, the conductive layer portion contacting the conductive fingers;
• and
• forming an interconnection structure on the front side of the semiconductor layer and including vias in contact with the fingers.