A pixel cell includes a photodiode disposed in a semiconductor material to accumulate image charge in response to incident light directed to the photodiode. A global shutter gate transistor disposed in the semiconductor material and is coupled to the photodiode to selectively deplete the image charge from the photodiode. A storage transistor is disposed in the semiconductor material to store the image charge. An optical isolation structure is disposed in the semiconductor material proximate to the storage transistor to isolate a sidewall of the storage transistor from stray light and stray charge in the semiconductor material outside of the storage transistor. The optical isolation structure is filled with tungsten.