A chamber member of a plasma source is provided and includes a sidewall, a transition member, a top wall and an injector connecting member. The sidewall is cylindrically-shaped and surrounds an upper region of a substrate processing chamber. The transition member is connected to the sidewall. The top wall is connected to the transition member. The injector connecting member is connected to the top wall, positioned vertically higher than the sidewall, and configured to connect to a gas injector. Gas passes through the injector connecting member via the gas injector and into the upper region of the substrate processing chamber. A center height to low inner diameter ratio of the chamber member is 0.25-0.5 and/or a center height to outer height ratio of the chamber member is 0.4-0.85.