Disclosed is a method for manufacturing a CMOS image sensor, capable of preventing dopants implanted with high energy from penetrating into a lower part of a gate electrode when a photodiode is formed, thereby preventing current leakage of a transistor and variation of a threshold voltage. The method includes the steps of forming a gate electrode on a transistor area of a first conductive type semiconductor substrate including a photodiode area and the transistor area, forming a salicide layer on the gate electrode, and implanting second conductive type dopants for forming a photodiode in a photodiode area of the semiconductor substrate.