An apparatus and method for gas injection sequencing in order to increase the gas injection total pressure while satisfying an upper limit to the process gas flow rate, thereby achieving gas flow uniformity during a sequence cycle and employing practical orifice configurations. The gas injection system includes a gas injection electrode having a plurality of regions, through which process gas flows into the process chamber. The gas injection system further includes a plurality of gas injection plenums, each independently coupled to one of the aforesaid regions and a plurality of gas valves having an inlet end and an outlet end, where the outlet end is independently coupled to one of the aforesaid plurality of gas injection plenums. The gas injection system includes a controller coupled to the plurality of gas valves for sequencing the flow of process gas through the aforesaid plurality of regions.