A method of making a monolithic ceramic component of a gas delivery system of a semiconductor substrate processing apparatus wherein the gas delivery system is configured to supply process gas to a gas distribution member disposed downstream thereof. The gas distribution member is configured to supply the process gas to a processing region of a vacuum chamber of the apparatus, wherein the processing region is disposed above an upper surface of a semiconductor substrate to be processed. The method comprises preparing a green compact of ceramic material. The green compact of ceramic material is formed into a form of a desired monolithic ceramic component of the gas delivery system. The formed green compact of ceramic material is fired to form the monolithic ceramic component of the gas delivery system.