Cmos imager photodiode with enhanced capacitance

Abstract

A pixel sensor cell having a semiconductor substrate having a surface; a photosensitive element formed in a substrate having a non-laterally disposed charge collection region entirely isolated from a physical boundary including the substrate surface. The photosensitive element comprises a trench having sidewalls formed in the substrate of a first conductivity type material; a first doped layer of a second conductivity type material formed adjacent to at least one of the sidewalls; and a second doped layer of the first conductivity type material formed between the first doped layer and the at least one trench sidewall and formed at a surface of the substrate, the second doped layer isolating the first doped layer from the at least one trench sidewall and the substrate surface. In a further embodiment, an additional photosensitive element is provided that includes a laterally disposed charge collection region that contacts the non-laterally disposed charge collection region of the photosensitive element and underlies the doped layer formed at the substrate surface.