A method of treating a substrate includes disposing the substrate in a processing chamber having a first chamber portion configured to define a plasma space and a second chamber portion configured to define a process space, introducing a first gas to the plasma space and introducing a second gas to the process space. A plasma is formed in the plasma space from the first gas using a plasma source coupled to the upper chamber portion, and a process chemistry for treating the substrate is formed in the process space by providing a grid positioned between the first chamber portion and the second chamber portion such that the plasma can diffuse from the plasma space to the process space.