A process is provided for depositing an undoped silicon oxide film on a substrate disposed in a process chamber. A process gas that includes SiF₄, a fluent gas, a silicon source, and an oxidizing gas reactant is flowed into the process chamber. A plasma having an ion density of at least 10¹¹ ions/cm³ is formed from the process gas. The undoped silicon oxide film is deposited over the substrate with the plasma using a process that has simultaneous deposition and sputtering components.