Provided is an image sensor having a color filter. The image sensor includes a photoelectric conversion device formed in a semiconductor substrate. Interlayer insulating layers are laminated on an upper portion of the semiconductor substrate. The interlayer insulating layers defines an opening located on an upper portion of the photoelectric conversion device. A color filter is disposed in the opening, and a planarization layer fills the opening on the color filter. The planarization layer has a refractive index which is greater than an average refractive index of the interlayer insulating layers.