Visible and infrared image sensor

A method of image sensor fabrication, the method comprising:

• forming a second semiconductor layer on a back side of a first semiconductor layer;
• forming one or more groups of pixels disposed in a front side of the first semiconductor layer, the one or more groups of pixels including:
• a first portion of pixels, wherein the first portion of pixels are separated from the second semiconductor layer by a spacer region;
• a second portion of pixels, wherein a first doped region of the second portion of pixels is in contact with the second semiconductor layer, and wherein the first doped region is of a same majority charge carrier type as the second semiconductor layer;
• pinning wells separating individual pixels in the one or more groups of pixels, wherein the pinning wells extend through the first semiconductor layer;
• and
• deep pinning wells separating the one or more groups of pixels, wherein the deep pinning wells extend through the first and second semiconductor layers.