Photodiode with insulator layer along intrinsic region sidewall

A method comprising:

• forming a lower terminal in a substrate, the lower terminal including a first p-type well and an n-type well over the first p-type well;
• forming a trench into the substrate over the lower terminal;
• forming an intrinsic semiconductor region in the trench in contact with the lower terminal, wherein the insulator layer contacts the intrinsic semiconductor region along an entirety of a vertical extent of the intrinsic semiconductor region;
• forming an insulator layer along a sidewall of the intrinsic semiconductor region;
• forming a second p-type well in the substrate between the insulator layer and a transfer gate, wherein the n-type well extends between the first p-type well and the transfer gate;
• forming a transfer gate adjacent the intrinsic semiconductor region and a floating diffusion adjacent to the transfer gate, wherein the insulator layer is positioned between the intrinsic semiconductor region and the transfer gate;
• and
• forming an upper terminal in contact with the intrinsic semiconductor region.