Layout design to enhance the color sensitivity of the color pixel cell in CMOS color image sensing device

A layout design to enhance the color sensitivity of the color pixel cell in CMOS color image sensing device is disclosed, wherein the color pixel cell layout comprises four monochrome pixel blocks with the same size to form a color pixel cell in a 4-square structure. Two pixel blocks are green, one pixel block is red, the rest one is blue. Each monochrome pixel block is a photodiode having P/N junction. The shape and magnitude of the N-well doped on the P-type silicon substrate in each monochrome pixel block are adjusted, so that the two green pixel blocks have the depletion region with the largest total area when the photodiode is applied with a negative bias voltage. The blue pixel block has the depletion region with the secondary area, the red pixel block has the depletion region with the minimum area. The larger depletion region, the better absorption to light. The color pixel cell thereby has an increased absorption to green light and blue light, so that the color sensitivity of CMOS image sensor is enhanced.