Showerhead electrodes for a semiconductor material processing apparatus are disclosed. An embodiment of the showerhead electrodes includes top and bottom electrodes bonded to each other. The top electrode includes one or more plenums. The bottom electrode includes a plasma-exposed bottom surface and a plurality of gas holes in fluid communication with the plenum. Showerhead electrode assemblies including a showerhead electrode flexibly suspended from a top plate are also disclosed. The showerhead electrode assemblies can be in fluid communication with temperature-control elements spatially separated from the showerhead electrode to control the showerhead electrode temperature. Methods of processing substrates in plasma processing chambers including the showerhead electrode assemblies are also disclosed.