Abstract: A chemical vapor deposition process for depositing tungsten films having small grain size is provided. The process involves depositing a nucleation layer having very small nuclei that are closely spaced so that there are few vacancies on the surface. Such a nucleation layer results in a film with small grains after the subsequent deposition of bulk layers. The temperature of the substrate can be increased during deposition of the nucleation layer and then lowered for deposition of the bulk layer to produce a small grain tungsten film. Additionally, the thickness of the nucleation layer can be controlled, and the deposition chamber pressure and silage flow rates can also be controlled to achieve the desired nucleation layer before deposition of the bulk layers.