A microelectronic device contains a high voltage component having an upper plate and a lower plate. The upper plate is isolated from the lower plate by a main dielectric between the upper plate and low voltage elements at a surface of the substrate of the microelectronic device. A lower-bandgap dielectric layer is disposed between the upper plate and the main dielectric. The lower-bandgap dielectric layer contains at least one sub-layer of silicon nitride having a refractive index between 2.11 and 2.23. The lower-bandgap dielectric layer extends beyond the upper plate continuously around the upper plate. The lower-bandgap dielectric layer has an isolation break surrounding the upper plate at a distance of at least twice the thickness of the lower-bandgap dielectric layer from the upper plate.