Various embodiments of the present disclosure are directed towards an image sensor including a first photodetector and a second photodetector each disposed within a semiconductor substrate. An isolation structure extends from a front-side surface of the semiconductor substrate to a back-side surface of the semiconductor substrate. The front-side surface is opposite the back-side surface and the isolation structure is laterally between the first and second photodetectors. A readout transistor is disposed on the front-side surface of the semiconductor substrate. A first side of the readout transistor overlies the first photodetector and a second side of the readout transistor overlies the second photodetector. The first side is opposite the second side and the readout transistor continuously extends over the isolation structure.