A plasma processing apparatus may include a process chamber having an interior processing volume; a first RF coil to couple RF energy into the processing volume; a second RF coil to couple RF energy into the processing volume, the second RF coil disposed coaxially with respect to the first RF coil; and a third RF coil to couple RF energy into the processing volume, the third RF coil disposed coaxially with respect to the first RF coil, wherein when RF current flows through the each of the RF coils, either the RF current flows out-of-phase through at least one of the RF coils with respect to at least another of the RF coils, or the phase of the RF current may be selectively controlled to be in-phase or out-of-phase in at least one of the RF coils with respect to at least another of the RF coils.