A backside illumination (BSI) image sensor and a method of forming the same are provided. A method includes forming a plurality of photosensitive pixels in a substrate, the substrate having a first surface and a second surface, the second surface being opposite the first surface, the substrate having one or more active devices on the first surface. A first portion of the second surface is protected. A second portion of the second surface is patterned to form recesses in the substrate. An anti-reflective layer is formed on sidewalls of the recesses. A metal grid is formed over the second portion of the second surface, the anti-reflective layer being interposed between the substrate and the metal grid.