Abstract: An edge seal structure and fabrication method are described. The edge seal structure includes a high impedance substrate containing a base material and a grounded floating edge seal that is on the substrate but is isolated from the base material. The edge seal contacts a first doped well in the substrate that has the same conductivity type as and is more heavily doped than the base material. The first doped well is in a second doped well that has a different conductivity type than the first doped well. The first and second doped wells and the base material form back-to-back series connected diodes. The wells are effectively connected to power and ground such that the diodes are reverse-biased. The edge seal is formed by a stack of conductive layers, at least some of which are surrounded by a stack of insulating layers.