An improved reflectivity optical grid for image sensors. In an embodiment, a backside illuminated CIS device includes a semiconductor substrate having a pixel array area comprising a plurality of photosensors formed on a front side surface of the semiconductor substrate, each of the photosensors forming a pixel in the pixel array area; an optical grid material disposed over a backside surface of the semiconductor substrate, the optical grid material patterned to form an optical grid that bounds each of the pixels in the pixel array area and extending above the semiconductor substrate, the optical grid having sidewalls and a top portion; and a highly reflective coating formed over the optical grid, comprising a pure metal coating of a metal that is at least 99% pure, and a high-k dielectric coating over the pure metal coating that has a refractive index of greater than about 2.0. Methods are also disclosed.