Disclosed are an image sensor and a method for manufacturing the same, capable of increasing a light absorbing coefficient by forming a rough surface on a photodiode. The image sensor includes a semiconductor substrate with a plurality of photodiodes thereon having rough upper surfaces, a dielectric layer on the semiconductor substrate, a color filter layer on the dielectric layer, a planarization layer on an entire surface of the semiconductor substrate including the color filter layer, and a plurality of micro-lenses formed on the planarization layer to correspond to the color filter layer.