Abstract: A back surface illuminated image sensor is provided. The back surface illuminated image sensor includes: a first passivation layer disposed on the photodiode array; an oxide grid disposed on the first passivation layer and forming a plurality of holes exposing the first passivation layer; a color filter array including a plurality of color filters filled into the holes, wherein the oxide grid has a refractive index smaller than that of plurality of color filters; and a metal grid aligned to the oxide grid, wherein the metal grid has an extinction coefficient greater than zero.