Patent attributes
First diffusion region constituting a photodiode in each pixel stores carriers generated according to incident light. Second diffusion region is formed at a surface of the first diffusion region to cover a peripheral part of the first diffusion region. In the peripheral part of the first diffusion region, crystal defects tend to occur by a process of forming an isolation region and a gate electrode, so that dark current noise tends to occur. The second diffusion region functioning as a protection layer prevents crystal defects in a manufacturing process. The second diffusion region isn't formed on a center of the surface of the first diffusion region where crystal defects don't tend to occur. In the first diffusion region where the second diffusion region isn't formed, the thickness of a depletion layer increases, which improves light detection sensitivity. This improves detection sensitivity of the photodiode without increasing the dark current noise.
