Image sensor and manufacturing method thereof

A semiconductor structure, comprising:

• a substrate comprising a first material, wherein the first material generates electrical signals from radiation within a first range of wavelengths;
• an image sensor element comprising a second material, wherein the second material generates electrical signals from radiation within a second range of wavelengths, the second range is different from first range;
• and
• a guard ring region proximal to the image sensor element and facing a light-receiving surface of the substrate.

A semiconductor structure, comprising:

• a substrate comprising a first material, wherein the first material generates electrical signals from radiation within a first range of wavelengths;
• an image sensor element comprising a second material, wherein the image sensor element is disposed in a recessed portion of the substrate, and the second material generates electrical signals from radiation within a second range of wavelengths, the second range is different from first range;
• a transparent layer proximal to a light receiving surface of the image sensor element, wherein the transparent layer is transparent to radiation within the second range of wavelength;
• and
• a plurality of microstructure portions at an interface between the substrate and the transparent layer.