An improved electrode for a p-type gallium nitride based semiconductor material is disclosed that includes a layer of an oxidized metal and a first and a second layer of a metallic material. The electrode is formed by depositing three or more metallic layers over the p-type semiconductor layer such that at least one metallic layer is in contact with the p-type semiconductor layer. At least two of the metallic layers are then subjected to an annealing treatment in the presence of oxygen to oxidize at least one of the metallic layers to form a metal oxide. The electrodes provide good ohmic contacts to p-type gallium nitride-based semiconductor materials and, thus, lower the operating voltage of gallium nitride-based semiconductor devices.