In this paper, we report on the deposition of amorphous silicon (a-Si:H) films at ultra-high growth rate (11–60?nm/s) by means of the expanding thermal plasma technique, followed by solid-phase crystallization (SPC). Large-grain (?1.5??m) polycrystalline silicon was obtained after SPC of high growth rate (?25?nm/s) deposited a-Si:H films. The obtained results are discussed by taking into account the impact of the a-Si:H microstructure parameter R* as well as of its morphology, on the final grain size development.