Abstract: A plasma reactor for processing a semiconductor substrate within a reactor chamber with a process gas from which a plasma has been formed in the chamber by electromagnetic excitation includes a sputter target in the chamber and overlying the wafer, the sputter target having additive material for the plasma, and a sputter excitation electrode overlying the target surface, the sputter excitation electrode having plural conductive segments separated by apertures therebetween, selected ones of the plural conductive segments being excited by an RF signal of a given phase and other of said plural conductive segments being excited by an RF signal of a different phase. Preferably, alternate segments are excited by RF signals of opposite phase, so that RF power radiated by alternate ones of the conductive segments is balanced by the RF power radiated by the remaining ones of the conductive segments. Preferably, segments excited by one phase are insulated from segments excited by the other phase.