a method for processing a substrate in a capacitively - coupled plasma processing system having a plasma processing chamber and at least an upper electrode and a lower electrode . the substrate is disposed on the lower electrode during plasma processing . the method includes providing at least a first rf signal , which has a first rf frequency , to the lower electrode . the first rf signal couples with a plasma in the plasma processing chamber , thereby inducing an induced rf signal on the upper electrode . the method also includes providing a second rf signal to the upper electrode . the second rf signal also has the first rf frequency , a phase of the second rf signal is offset from a phase of the first rf signal by a value that is less than 10 %, the method further includes processing the substrate while the second rf signal is provided to the upper electrode .