Microcrystalline Si (muc-Si) films have been deposited using five W wire filaments, 0.5 nun in diameter, for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD-grown films with and without modification of the initial growing layer by using a transformer-coupled plasma system. The W-wire filament temperature was maintained below 1600 degreesC to avoid metal contamination by thermal evaporation of the filament. Deposition conditions were varied, including the H-2 dilution ratio, with and without a seed-layer plasma treatment. From Raman analysis, we observed that the film crystallinity was strongly influenced by the H-2 dilution ratio and weakly depended on the distance between the wire and the substrate. We were able to achieve a crystalline volume fraction of approximately 79% with a H-2/SiH4 ratio of 80, a wire temperature of 1514 degreesC, a substrate distance of 4 cm, and a chamber pressure of 38 mtorr. We investigated the influence of a plasma treatment during the initial stage of Si film, formation for property variations in the HWCVD-grown muc-Si film. This article also deals with the influence of the H-2 dilution ratio in crystallinity modification.