A method of fabricating an image sensor includes forming a pixel array in an imaging region of a semiconductor substrate and forming a trench in a peripheral region of the semiconductor substrate after forming the pixel array. The peripheral region is on a perimeter of the imaging region. The trench is filled with an insulating material. An interconnect layer is formed after filling the trench with insulating material. A first wafer is bonded to a second wafer. The first wafer includes the interconnect layer and the semiconductor substrate. A backside of the semiconductor substrate is thinned to expose the insulating material. A via cavity is formed through the insulating material. The via cavity extends down to a second interconnect layer of the second wafer. The via cavity is filled with a conductive material to form a via. The insulating material insulates the conductive material from the semiconductor substrate.