A CMOS image sensor for improving light sensitivity and peripheral brightness ratio, and a method for fabricating the same. The CMOS image sensor includes a substrate on which a light sensor and device isolating insulation films are formed, in which the top of the substrate is coated with a plurality of metal layers and oxide films; a plurality of reflective layers formed inside the metal layers, each being spaced apart; a color filter embedded in a groove formed by etching the oxide films inside the reflective layers by a predetermined thickness; a plurality of protrusions formed on both sides of the top of the color filter, each arranged at a predetermined distance from one another; a flat layer formed on the top of the protrusions and the oxide films; and a micro-lens formed on the top of the flat layer. The reflective layer disposed at the top of the photodiode is made of a material having a high reflectance and low absorptivity. Therefore, light incident on the virtual focus plane on the top portion of the reflective layer converges on the photodiode, and thus, the light sensitivity of the sensor is greatly improved.