Cmos image sensor having front side and back side trench isolation structures enclosing pixel regions and a capacitor for storing the image charge

Abstract

Examples of the disclosed subject matter propose disposing trench isolation structure around the perimeter of the pixel transistor region of the pixel cell. The trench isolation structure includes front side (e.g., shallow and deep) trench isolation structure and back side deep trench isolation structure that abut against or contacts the bottom of front side deep trench isolation structure for isolating the pixel transistor channel of the pixel cell's pixel transistor region. The formation and arrangement of the trench isolation structure in the pixel transistor region forms a floating doped well region, containing, for example, a floating diffusion (FD) and source/drains (e.g., (N) doped regions) of the pixel transistors. This floating P-well region aims to reduce junction leakage associated with the floating diffusion region of the pixel cell.