A Field Effect Transistor (FET) structure having: a semiconductor; a first electrode structure; a second electrode structure; and a third electrode structure for controlling a flow of carriers in the semiconductor between the first electrode structure and the second electrode structure; a dielectric structure disposed over the semiconductor and extending horizontally between first electrode structure, the second electrode structure and the third electrode structure; and a fourth electrode passing into the dielectric structure and terminating a predetermined, finite distance above the semiconductor for controlling an electric field in the semiconductor under the fourth electrode structure.