Automatic formation of Al interconnects and ring electrodes, fully encapsulated by alumina, in planar arrays of Al₂O₃/Al/Al₂O₃ microcavity plasma devices has been accomplished by electrochemical processing of Al foil. Following the fabrication of cylindrical microcavities (50–350 µm in diameter) in 127 µm thick Al foil, virtually complete anodization of the foil yields azimuthally symmetric Al electrodes surrounding each cavity and interconnects between adjacent microcavities that are produced and simultaneously buried within a transparent Al₂O₃ film without the need for conventional patterning techniques. The diameter and pitch of the microcavities prior to anodization, as well as the anodization process parameters, determine which of the microcavity plasma devices in a one- or two-dimensional array are connected electrically. Data presented for 200 µm diameter cavities with a pitch of 150–225 µm illustrate the patterning of the interconnects and electrode connectivity after 4–10 h of anodization in oxalic acid. Self-patterned, linear arrays comprising 25 dielectric barrier devices have been excited by a sinusoidal or bipolar pulse voltage waveform and operated in 400–700 Torr of rare gas. Owing to the electrochemical conversion of most of the Al foil into Al₂O₃, the self-formed arrays exhibit an areal capacitance ~82% lower than that characteristic of previous Al/Al₂O₃ device arrays (Park et al 2006 J. Appl. Phys. 99 026107).