An image sensor includes a semiconductor substrate, a plurality of photoelectric transducer devices, a dielectric isolating structure and a plurality of spacers. The semiconductor substrate has a backside surface and a front side surface opposite to the backside surface. The photoelectric transducer devices are disposed on the front side surface. The dielectric isolating structure extends downwards into the semiconductor substrate from the front side surface and penetrates through the backside surface, so as to from a grid structure and isolate the photoelectric transducer devices from each other. The spacers are disposed on a plurality of sidewalls of the grid structure.