Prismatic polymer monolithic capacitor structure operating at temperatures exceeding 140° C. and including multiple interleaving radiation-cured polymer dielectric layers and metal layers. Method for fabrication of same. The geometry of structure is judiciously chosen to increase sheet resistance of metal electrodes while reducing the capacitor's equivalent series resistance. Metal electrode layers are provided with a thickened peripheral portion to increase strength of terminating connections and are passivated to increase corrosion resistance. Materials for polymer dielectric layers are devised to ensure that the capacitor's dissipation factor remains substantially unchanged across the whole range of operating temperatures, to procure glass transition temperature that is no less than the desired operating temperature, and to optimize the absorption of ambient moisture by the polymeric layers.