Membrane-mediated electropolishing (MMEP) is a method for planarizing and polishing a metal anode using a charge-selective ion-conducting membrane to separate the cathode and electrolyte solution from a thin layer of deionized water covering the substrate. Unlike conventional electropolishing, the current density and rate of material removal are controlled by ohmic resistance of the interfacial water layer. By controlling the interfacial pressure and tangential velocity of the membrane with respect to the substrate, the principles of lubrication mechanics can be used to maintain the thickness of the water layer at much less than 1 mu m, thereby providing a high efficiency for planarizing submicrometer topographic features. This paper describes the process characterization and applications of MMEP for planarizing Cu substrates such as test wafers for the fabrication of Cu damascene circuitry on integrated circuits. (C) 2008 The Electrochemical Society.