A CMOS image sensor with improved sensitivity includes a main pixel array region of an active pixel array region formed on a semiconductor substrate. A passivation layer is formed over the sensor, and it is at least partially removed from the main pixel array region, such that incident light being detected by the main pixel array does not pass through the passivation layer. Optical absorption and refraction caused by the material of the passivation layer are eliminated, resulting in an image sensor with improved optical sensitivity.