The thin film polycrystalline silicon solar cells have been fabricated on inactive P/sup ++/ mono-crystalline silicon substrates by rapid thermal CVD technique. With the graphite boat covered by pyrogenative graphite layer, the quality of the growth layer has been increased. By varying the thickness of the active layer, the best result was obtained at the thickness of 37 /spl mu/m with a 2 /spl mu/m depth p/sup ++/ buffer layer deposited simultaneously. The fill factor could be improved by a suitable annealing in forming gas ambience. The best conversion efficiency of 15.12% (AM1.5G, 24.5/spl deg/C )has been achieved without cell's surface texture.