An embodiment of the invention IS an array of microcavity plasma devices The array includes a first metal film electrode with a plurality of non-uniform cross-section microcavities therein that are encapsulated in oxide A second electrode is a thin metal foil encapsulated in oxide that is bonded to the first electrode A packaging layer contains gas or vapor in the non-uniform cross-section microcavities To make such device, photoresist is patterned to encapsulate the anodized foil or film except on a top surface at desired positions of microcavities A second anodization or electrochemical etching is conducted to form the non-uniform cross-section sidewall microcavities cavities After removing photoresist and metal oxide, a final anodization lines the walls of the microcavities with metal oxide and fully encapsulates the metal electrodes with metal oxide.