US Patent 7642579 Image sensor comprising pixels with one transistor

A pixel having a MOS-type transistor formed in and above a semiconductor substrate of a first doping type, a buried semiconductor layer of a second doping type being placed in the substrate under the MOS transistor and separated therefrom by a substrate portion forming a well. The buried semiconductor layer comprises a thin portion forming a pinch area placed under the transistor channel area and a thick portion placed under all or part of the source/drain areas of the transistor.