Device over photodetector pixel sensor

A method for forming an integrated chip comprising:

• forming a photodetector in a semiconductor substrate;
• forming a transfer transistor on the semiconductor substrate, wherein the transfer transistor overlies and is electrically coupled to the photodetector;
• forming a semiconductor mesa elevated relative to the transfer transistor;
• depositing a conductive layer covering the semiconductor mesa;
• forming a via extending through the conductive layer to the transfer transistor, wherein the via electrically couples the conductive layer to the transfer transistor;
• and
• patterning the conductive layer to form a gate electrode on the semiconductor mesa after the forming of the via.

A method for forming an integrated chip comprising:

• forming a pixel on a frontside of a semiconductor substrate, wherein the pixel comprises a photodetector in the semiconductor substrate and further comprises a transfer transistor electrically coupled to the photodetector;
• forming a readout transistor on the frontside and electrically coupled to the transfer transistor, wherein the readout transistor is spaced from the semiconductor substrate;
• patterning a backside of the semiconductor substrate, opposite the frontside, to form a trench extending through the semiconductor substrate, wherein the trench and the readout transistor overlap along a vertical axis;
• and
• filling the trench with dielectric material.