Pixel cell and imaging system with cell deep trench isolation structure for near infrared improvement

A pixel cell includes a photodiode disposed in a pixel cell region and proximate to a front side of a semiconductor layer to generate image charge in response to incident light directed through a backside to the photodiode. A cell deep trench isolation (CDTI) structure is disposed in the pixel cell region along an optical path of the incident light to the photodiode and proximate to the backside. The CDTI structure includes a central portion extending a first depth from the backside towards the front side. Planar outer portions extend laterally outward from the central portion. The planar output portions further extend a second depth from the backside towards the front side. The first depth is greater than the second depth. Planes formed by each of the planar outer portions intersect in a line coincident with a longitudinal center line of the central portion of the CDTI structure.