A plasma reactor includes a chamber body having an interior space that provides a plasma chamber, a gas distribution port to deliver a processing gas to the plasma chamber, a workpiece support to hold a workpiece, an antenna array comprising a plurality of monopole antennas extending partially into the plasma chamber, and an AC power source to supply a first AC power to the plurality of monopole antennas. The plurality of monopole antennas are divided into a plurality of groups of monopole antennas, and the AC power source is configured to generate AC power on a plurality of power supply lines at a plurality of different phases, and different groups of monopole antennas are coupled to different power supply lines.