A method and apparatus are provided for plasma-based processing of a substrate based on a plasma source having a first, second and third electrodes disposed above a pedestal. The second electrode is disposed between the first and third electrodes. A first gap is formed between the first electrode and the pedestal and between the third electrode and the pedestal. A second gap is formed between the first and second electrodes, and a third gap is formed between the second and third electrodes. A first radio frequency (RF) power supply is connected to the first and third electrodes and is configured to predominantly deliver power to plasmas located in the first gap. A second RF power supply is connected to the second electrode and is configured to predominantly deliver power to plasmas located in the second and third gaps. In such a configuration, the power density of the plasmas located in the first gap can be independently controlled relative to the power density of the plasmas located in the second and third gaps.