Image sensing module, camera module and electronic device

An image sensing module comprising:

• a circuit substrate having:
• an upper surface;
• a lower surface disposed opposite to the upper surface;
• an opening surface connected to the upper surface and the lower surface;
• and
• an opening located at the opening surface;
• an optical flat element fixed on the upper surface of the circuit substrate, wherein the optical flat element is disposed corresponding to the opening of the circuit substrate;
• a sensing element disposed on the lower surface of the circuit substrate, wherein the opening of the circuit substrate is located between the sensing element and the optical flat element, the sensing element and the optical flat element form an air gap therebetween, and the opening surface surrounds the air gap;
• and
• a plurality of metal protrusions disposed between the circuit substrate and the sensing element, wherein each of the plurality of metal protrusions is electrically connected to the circuit substrate and the sensing element;
• wherein the image sensing module further comprises at least one anti-reflection layer disposed on at least one surface at the air gap, the at least one anti-reflection layer comprises:
• a plurality of nano-ridge structures extending along a direction from the at least one surface at the air gap towards the air gap, wherein the plurality of nano-ridge structures are irregularly arranged.