In a method for forming a semiconductor device photo-sensing regions are formed over a frontside of a substrate. A first layer is formed over a backside of the substrate and is patterned to form a plurality of grid lines. The grid lines can define a plurality of first areas and a plurality of second areas. A second layer may be formed over exposed portions of the backside, the gridlines, the first areas, and the second areas and a third layer may be formed over the second layer. The second and third layer may have different etch rates and the third layer is pattern so as to remove the third layer from over the plurality of first areas.