A plasma processing apparatus includes a chamber having a support for a substrate, and at least one gas inlet into the chamber. The apparatus is configured to alternately introduce an etch gas and a deposition gas into the chamber through the at least on gas inlet, and to strike a plasma into the etch gas and the deposition gas alternately introduced into the chamber. The apparatus is further equipped with an attenuation device for reducing and/or homogenizing the ion flux from the plasma substantially without affecting the neutral radical number density.