Low temperature growth of hydrogenated nanocrystalline silicon film (nc-Si:H) by microwave electron cyclotron resonance chemical vapor deposition has been performed employing a double dilution of silane, using a He carrier for SiH4 and its subsequent dilution by H2. A series of Raman spectra and AFM pictures has shown that a very thin (<100Å) nc-Si:H layer initially grown with high H2 dilution on a glass substrate can serve as a seed layer for the subsequent growth of the film with lower H2 dilution, which results in a higher crystallinity of the whole film. The role of this thin layer in low temperature junction formation has been examined by the insertion of the layer between the interface of both nc-Si:H (deposited with lower H2 dilution)/c-Si and a-Si:H/c-Si heterojunction type photovoltaic cells. This is to address the knowledge that the device's performance is strongly influenced by the quality of the thin film silicon/crystalline silicon interface. Various thicknesses and H2 dilution ratios have been used to find the optimized condition providing the best performance of the cells. The maximum efficiency of 10.5% (Jsc=35.1mA/cm2, Voc=0.51V and FF=0.59) has been obtained, without an AR coating, by the successive deposition of nc-Si:H film with four different H2 dilution ratios on a crystalline silicon substrate. This is potentially a low-temperature, low-cost solar cell fabrication process.