An image sensor comprises: an array of photoelectric conversion elements in a substrate, the photoelectric conversion elements being arranged in rows and columns extending in a first direction and a second direction respectively; a plurality of first junction isolation regions in the substrate that each isolate side portions of neighboring photoelectric conversion elements of a common row, and a plurality of second junction isolation regions in the substrate that each isolate side portions of neighboring photoelectric conversion elements of a common column; and a plurality of dielectric isolation regions in the substrate, that each isolate corner portions of neighboring photoelectric conversion elements. In one embodiment, the photoelectric conversion elements have a first pitch in the first direction and have a second pitch in the second direction and the first pitch is substantially equal for the photoelectric conversion elements of a common row, and the second pitch is substantially equal for the photoelectric conversion elements of a common column.