White-infra-red image sensor having unit pixel with vertically stacked arrangement of photoelectric conversion regions

A unit pixel, comprising:

• a substrate having a light-receiving side and a front side;
• a first photoelectric conversion region, disposed in the substrate, configured to convert a first component of incident light within a first light wavelength range to generate a first charge;
• a second photoelectric conversion region, disposed in the substrate, configured to convert a second component of the incident light within a second wavelength range to a second charge;
• a first floating diffusion region, disposed in the substrate;
• a first gate region, disposed on the front side of the substrate and positioned over the first floating diffusion region and the first photoelectric conversion region, configured to control transfer of the first charge from the first photoelectric conversion region to the first floating diffusion region by providing a channel therebetween;
• a second floating diffusion region, disposed in the substrate;
• and
• a second gate region, disposed on the front side of the substrate and positioned over the second floating diffusion region and the second photoelectric conversion region, configured to control transfer of the second charge from the second photoelectric conversion region to the second floating diffusion region by providing a channel therebetween;
• wherein the second photoelectric conversion region is interposed between the first photoelectric conversion region and the light-receiving side of the substrate;
• and the first photoelectric conversion region and the second photoelectric conversion region are spaced apart by a gap region.