A substrate processing system is provided with a processing chamber, an alternating voltage supply, and an impedance matching network. The processing chamber holds a substrate during processing and the alternating voltage supply is connected with the processing chamber to capacitively couple energy to a plasma formed within the processing chamber. The impedance matching network is coupled with the alternating voltage supply and has a variable resistive element and a variable reactive element, whose states respectively define distinct real and imaginary parts of an impedance.