An integrated circuit structure comprises a bottom dielectric layer on a substrate, a middle dielectric layer, and a top dielectric layer. The middle dielectric layer has a top surface and a bottom surface, and comprises a plurality of materials. Respective concentration profiles for at least two of the plurality of materials between the top and bottom surfaces are non-uniform and arranged to induce a variation in energy gap between the top and bottom surfaces. The variation in energy gap establishes an electric field between the top and bottom surfaces tending to oppose charge motion toward at least one of the top and bottom surfaces and prevent resultant charge leakage.