The present disclosure provides a backside illuminated semiconductor
device. The device includes a substrate having a front surface and a back
surface; a plurality of sensor elements formed in the substrate, each of
the plurality of sensor elements is designed and configured to receive
light directed towards the back surface; and a sensor isolation feature
formed in the substrate, and disposed horizontally between two adjacent
elements of the plurality of sensor elements, and vertically between the
back surface and the front surface.