An apparatus for depositing film stacks in-situ (i.e., without a vacuum break or air exposure) are described. In one example, an apparatus configured to deposit a plurality of film layers having different compositions on a substrate without exposing the substrate to a vacuum break between film deposition phases, is provided. The apparatus includes a process chamber, a plasma source and a process station reactant feed fluidically coupled to a gas inlet of the process station, and fluidically coupled to an inert gas delivery line, a first reactant mixture gas delivery line and a second reactant mixture gas delivery line such that the first reactant gas mixture and the second reactant gas mixture can be introduced sequentially into the process station reactant feed, and supplied via a shared path to the process station.