Plasma source assemblies comprising a housing with an RF hot electrode and a return electrode are described. The housing includes a gas inlet and a front face defining a flow path. The RF hot electrode includes a first surface oriented substantially parallel to the flow path. The return electrode includes a first surface oriented substantially parallel to the flow path and spaced from the first surface of the RF hot electrode to form a gap. Processing chambers incorporating the plasma source assemblies and methods of using the plasma source assemblies are also described.