Using in ultrahigh-vacuum (UHV) system, we could form polycrystalline silicon films. Polycrystalline silicon (poly-Si) films are formed on glass at substrate temperature below 550°C. We used two methods of crystallization. One is asdeposited polycrystalline Si by an UHV sputtering method and the other is solid-phase crystallization (SPC) of silicon film in UHV conditions. As-deposited poly-Si is oriented to (220) and SPC poly-Si is oriented to (111). The crystallinity is improved by increasing film thickness in as-deposited poly-Si film. Ar atoms, which are used for sputtering, disturb the crystallization. Ar concentration in SPC poly-Si is influenced by annealing pressure and surface conditions of Si film. Oxide layer on Si film disturbs SPC. The field effect mobility, 18 cm²/Vs, was obtained by a SPC poly-Si TFT.