Metastable &bgr;‐tungsten was identified, using transmission electron microscopy, in arrays of low pressure chemical vapor deposited contacts on patterned silicon wafers. In contrast, only &agr;‐tungsten was found in films deposited onto bare silicon wafers under identical conditions. Thus, we have shown that contact wells etched through oxide can play a role in determining which tungsten phase is deposited by low pressure chemical vapor deposition. This effect was observed for a variety of furnace conditions (T=300–330 °C, H2/WF6=150:1–400:1). Transmission electron micrographs and selected area diffraction patterns are presented which illustrate the microstructural differences between the &agr;‐ and &bgr;‐tungsten phases. Possible sources of oxygen or fluorine, impurities which are believed to stabilize &bgr;‐tungsten, are discussed and related to the geometry of the vias cut through oxide on patterned wafers.