Patent ID: 8357984

Claim:
An image sensor, comprising: an array of complementary metal-oxide-semiconductor (“CMOS”) pixels disposed in or on an epitaxial layer having a backside and a frontside, wherein metalization layers are disposed on the frontside, wherein a plurality of the pixels each includes: a photodiode region disposed in the epitaxial layer; frontside wells of a first polarity disposed in the epitaxial layer adjacent to either side of the photodiode region, the frontside wells of the first polarity forming charge carrier barrier regions between adjacent CMOS pixels of the array, and the frontside wells of the first polarity having an associated depth with respect to the frontside; a region of a second polarity disposed in the epitaxial layer below the photodiode region, the region of the second polarity being disposed at least in part in a region of the epitaxial layer that is deeper than the depth of the frontside wells of the first polarity; and first and second backside wells of the first polarity disposed within the epitaxial layer and extending up from the backside of the epitaxial layer, wherein the region of the second polarity extends horizontally from the first backside well to the second backside well and contacts both the first and second backside wells, wherein the region of the second polarity comprises a region having a single dopant concentration extending vertically from the photodiode region to the backside of the epitaxial layer.