A method of depositing tungsten over a substrate includes disposing the substrate into a vacuum enclosure of a tungsten deposition apparatus, performing a first tungsten deposition process that deposits a first tungsten layer over a physically exposed surface of the substrate by flowing a fluorine-containing tungsten precursor gas into the vacuum enclosure, performing an in-situ oxidation process by exposing the first tungsten layer to an oxidation agent gas while the substrate remains within the vacuum enclosure without breaking vacuum and forming a tungsten oxyfluoride gas which is pumped out of the vacuum enclosure, and performing a second tungsten deposition process that deposits a second tungsten layer on the first tungsten layer by flowing the fluorine-containing tungsten precursor gas into the vacuum enclosure in a second tungsten deposition process after the in-situ oxidation process.