A gas delivery apparatus for supplying process gas to a processing chamber of a plasma processing apparatus includes a mixing manifold having a plurality of gas inlets on a surface thereof, the gas inlets being equally spaced from a center mixing point of the mixing manifold; and optionally a plurality of gas supplies in communication with the plurality of gas inlets on the surface of the mixing manifold. A method of supplying gas to a processing chamber of a plasma processing apparatus using such a gas delivery apparatus involves providing a plurality of gas supplies in communication with a plurality of gas inlets on a surface of a mixing manifold; flowing at least two different gases from the plurality of gas supplies to the mixing manifold to create a first mixed gas; and supplying the first mixed gas to a plasma processing chamber coupled downstream of the mixing manifold.