A semiconductor structure includes a substrate, a barrier layer disposed over the substrate, a grid disposed over the barrier layer, and a first color filter disposed over the barrier layer. The semiconductor structure also includes a second color filter disposed over the substrate and laterally surrounded by and contacting the grid. The semiconductor structure further includes a dielectric layer disposed between the barrier layer and the substrate. The barrier layer includes an upper surface overlapping the grid and the first color filter and a bottom surface substantially level with a bottom surface of the second color filter. The dielectric layer includes a first portion overlapping a bottom surface of the first color filter and a second portion overlapping a bottom surface of the second color filter, wherein non-visible light is allowed to pass from the second color filter to the substrate through the second portion of the dielectric layer.