A bonding pad structure for an image sensor device and a method of fabrication thereof. The image sensor device has a radiation-sensor region including a substrate and a radiation detection device, and a bonding pad region including the bonding pad structure. The bonding pad structure includes: an interconnect layer; an interlayer dielectric layer (IDL), both layers extending from under the substrate into the bonding pad region; an isolation layer formed on IDL; a conductive pad having a planar portion and one or more bridging portions extending perpendicularly from the planar portion, through the IDL and isolation layers, and to the interconnect layer; and a plurality of non-conducting stress-releasing structures disposed between the isolation layer and the conductive pad in such a way to adjoin its planar and the bridging portions together for releasing potential pulling stress applied thereon and preventing a conductive pad peeling.