Method for manufacturing a CMOS image sensor

A method for manufacturing a CMOS image sensor having a photodiode, a transfer transistor, a reset transistor, a drive transistor and a select transistor, the method comprising:

• forming a device isolation layer on a device isolation region of a first conductive type substrate in which an active region and the device isolation region are defined;
• forming gate electrodes for the transfer transistor, the reset transistor, the drive transistor and the select transistor on the active region with gate insulating layers interposed therebetween;
• forming a first diffusion region of a second conductive type in a first region of the active region;
• and
• forming a second diffusion region in a floating diffusion region between the transfer transistor and the reset transistor by implanting impurity ions only into the floating diffusion region at a concentration lower than that of the first diffusion region,
• wherein the first diffusion region of the second conductive type is not formed in the floating diffusion region and a photodiode region.