High capacitance value capacitors are formed using bimetal foils of an aluminum layer attached to a copper layer. The copper side of a bimetallic copper/aluminum foil or a monometallic aluminum foil is temporarily protected using aluminum or other materials, to form a sandwich. The exposed aluminum is treated to increase the surface area of the aluminum by at least one order of magnitude, while not attacking any portion of the protected metal. When the sandwich is separated, the treated bimetal foil is formed into a capacitor, where the copper layer is one electrode of the capacitor and the treated aluminum layer is in intimate contact with a dielectric layer of the capacitor.