Image sensor with high quantum efficiency

A structure, comprising:

• a semiconductor layer having a first surface and a second surface opposite to the first surface;
• a first radiation sensing region disposed within the second surface of the semiconductor layer;
• a second radiation sensing region disposed within the second surface of the semiconductor layer;
• a metal layer having a groove structure over the first radiation sensing region;
• and
• a passivation layer over the groove structure, wherein the metal layer is between the passivation layer and the first radiation sensing region.

An image sensing device, comprising:

• a semiconductor layer having a first surface and a second surface opposite to the first surface;
• an interconnect structure disposed over the first surface of the semiconductor layer;
• first and second radiation sensing regions disposed within the second surface of the semiconductor layer;
• a metal stack, over the second surface of the semiconductor layer, to mask the second radiation sensing region;
• and
• a passivation layer over the second surface of the semiconductor layer, wherein the metal stack is disposed between the passivation layer and the first and second radiation sensing region.