High voltage capacitor

A high voltage capacitor integrated monolithically on a semiconductor structure comprising, from the bottom up:

• a diffusion region disposed in the semiconductor substrate;
• a gate oxide layer disposed over the diffusion region;
• a first layer of polycrystalline silicon disposed over the gate oxide layer;
• an interpoly dielectric layer;
• and
• a second layer of polycrystalline silicon disposed over the interpoly dielectric layer such that two series-connected, elementary capacitors are formed having a first common conductive plate which is formed in the second layer of polycrystalline silicon, and each elementary capacitor having a second conductive plate formed in the first layer of polycrystalline silicon below the first common conductive plate and including said interpoly dielectric layer as an isolation dielectric between the first common conductive plate and the second conductive plates, the diffusion region being coupled capacitively to a first one of the second conductive plates and electrically connected to a second one thereof, the second conductive plates being structurally independent of and isolated from each other, the high voltage capacitor having a first terminal on a first of the second conductive plates and a second terminal on a second of the second conductive plates, and the first common conductive plate is floating.