An apparatus and associated method for an energy-storage device (e.g., a capacitor) having a plurality of electrically conducting electrodes including a first electrode and a second electrode separated by a non-electrically conducting region, and wherein the non-electrically conducting region further includes a non-uniform permittivity (K) value. In some embodiments, the method includes providing a substrate; fabricating a first electrode on the substrate; and fabricating a second electrode such that the second electrode is separated from the first electrode by a non-electrically conducting region, wherein the non-electrically conducting region has a non-uniform permittivity (K) value. The capacitor devices will find benefit for use in electric vehicles, of all kinds, uninterruptible power supplies, wind turbines, mobile phones, and the like requiring wide temperature ranges from several hundreds of degrees C. down to absolute zero, consumer electronics operating in a temperature range of −55 degrees C. to 125 degrees C.