A storage transistor with a storage region is disposed in a semiconductor material. A gate electrode is disposed in a bottom side of an interlayer proximate to the storage region, and a dielectric layer is disposed between the storage region and the gate electrode. An optical isolation structure is disposed in the interlayer and the optical isolation structure extends from a top side of the interlayer to the gate electrode. The optical isolation structure is also adjoining a perimeter of the gate electrode and contacts the gate electrode. A capping layer is disposed proximate to the top side of the interlayer and the capping layer caps a volume encircled by the optical isolation structure.