A plasma reaction chamber particularly configured for chemical vapor deposition of titanium nitride with a TDMAT precursor, the deposition including a plasma step. Gas is injected from a gas cavity in a showerhead electrode assembly through a large number of showerhead holes into the processing region over the wafer. The showerhead electrode is capable of being RF energized to create a plasma of a gas in the processing region. The showerhead electrode and other parts of the assembly are cooled by a cooling plate disposed above the gas cavity and connected to a rim of the showerhead electrode. A convolute water-cooling channel is formed in the cooling plate having a small cross section and numerous bends so as to create turbulent flow, thus aiding thermal transfer. The water cooling plate is connected to the showerhead electrode across a large horizontal interface, thus also aiding thermal flow. An edge ring assembly is positioned in a peripheral recess at the top of heater pedestal supporting the wafer next to the processing region. The showerhead is insulated from the chamber body by an isolator having a downwardly sloping lower surface facing the processing region. Thereby, the isolator by itself or in combination with a plasma confinement ring around the wafer confines the plasma to the process area and induces the exhaust to flow downwardly from the processing region. The assembly includes a Z-shaped heat shield disposed between the walls of the recess and of the pedestal side and other parts of the ring assembly with gaps between the various members, thereby promoting thermal isolation in the edge region as well as protecting the side of the pedestal.