a lens array containing a plurality of microlenses arranged in a two-dimensional matrix;

a color filter array formed underneath the lens array and including a plurality of open window cells and a plurality of color filter cells, each of said open window cells and color filter cells corresponding to one microlens of the lens array, wherein each open window cell is adapted to pass red, green and blue lights, while each color filter cell is adapted to pass a predetermined color light;

a protection layer formed of dielectric material underneath the color filter array; and

a pixel sensor array formed underneath the protection layer and having

a first photosensor for sensing a first light passed through each color filter cell,

a second photosensor formed under the first photosensor for sensing a second light passed through each color filter cell,

a third photosensor for sensing a third light passed through each open window cell, and

a fourth photosensor formed under the third photosensor for sensing a fourth light passed through each open window cell;

wherein the pixel sensor array comprises:

a base substrate formed of P-type semiconductor material;

an epitaxial layer formed of P-type semiconductor on the base substrate;

a first photowell layer having a plurality of first photowell areas formed of N-type semiconductor material at a predetermined first depth from an upper surface of the epitaxial layer, wherein each of the first photowell areas forms the first photosensor and the third photosensor via P-N junction with the epitaxial layer; and

a second photowell layer having a plurality of second photowell areas formed of N-type semiconductor material at a predetermined second depth deeper than the first depth from the upper surface of the epitaxial layer, wherein each of the second photowell areas overlaps with one of the first photowell areas and forms the second photosensor and the fourth photosensor via P-N junction with the epitaxial layer.