Provided is an image sensor device. The image sensor device includes a substrate having a front side and a back side. The image sensor also includes an isolation feature disposed in the substrate. The image sensor further includes a radiation-sensing region disposed in the substrate and adjacent to the isolation feature. The radiation-sensing region is operable to sense radiation projected toward the radiation-sensing region from the back side. The image sensor also includes a transparent conductive layer disposed over the back side of the substrate.