A method of processing a workpiece in a plasma reactor includes coupling RF power from at least three RF power source of three respective frequencies to plasma in the reactor, setting ion energy distribution shape by selecting a ratio between the power levels of a first pair of the at least three RF power sources, and setting ion dissociation and ion density by selecting a ratio between the power levels of a remaining one of the three RF power sources and an applied magnetic field. The three respective frequencies can be an LF frequency, an HF frequency and a VHF frequency, wherein the first pair corresponds to the LF and HF frequencies and the second pair corresponds to the HF and VHF frequencies.