Hydrogenated microcrystalline silicon films were prepared by plasma enhanced chemical vapor deposition using an Ar-diluted $SiH_4$ gas at various deposition conditions. The substrate temperature and RF power were varied from 150 to $400\,^\circ\!C$ and 10 to 120 W, respectively. Structure and microstructure were examined by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Hydrogen bonding and optical properties were investigated by FTIR spectra and UV transmission spectra. The crystal fraction of the films increased as the deposition temperature decreased and RF power increased. More definite columnar morphology was developed with increasing the crystal fraction. The existence of $\mu$c-Si above a critical RF power ($> 30 W$) suggests that $SiH_2$ radical in plasma plays an important role for the formation of columnar morphology and uc-Si. The IR absorption analysis showed that the $SiH_2/SiH$ bonding ration in the silicon films increased as the crystal fraction increases. The UV absorption coefficient of the films became smaller as the deposition temperature and RF power increased. The effect of substrate temperature on the recrystallization of amorphous silicon films deposited by plasma enhanced chemical vapor deposition was investigated. The substrate temperature was varied from 200 to $400\,^\circ\!C$ and the recrystallization was carried out by annealing at $600\,^\circ\!C$ in nitrogen. The recrystallization proceeded through growth of the nuclei after an incubation time. As the substrate temperature increased, the incubation time was decreased and both the nucleation rate and growth rate were increased. The nucleation rate depended on the structural disorder caused by evolution of hydrogen contained in films during crystallization process. The grain size which was dominated by nucleation rate was decreased with increasing substrate temperature. The obtainable maximum grain size from the $1000\mbox{\AA}$ amorphous silicon in this temperature range was about $1.1 $\mu m$. We investigated the recrystallization behavior of $1000\mbox{\AA}$ a-Si films deposited by PECVD at various temperatures and were abled to enhance the grain size of the recrystallized polysilicon films using double layers of a-Si films. The deposition temperature of monolayer a-Si films varied from 200 to $400\,^\circ\!C$ and the films were recrystallized at $600\,^\circ\!C$ in nitrogen. As the deposition temperature increased, the incubation time was decreased and both the nucleation rate and growth rate were increased. Especially, the nucleation rate strongly depended on the deposition temperature. Since the $Si-SiO_2$ interface provides a large number of nucleation sites, it is desirable to suppress nucleation at the interface. As an idea we employed a double layer a-Si films. The lower a-Si layer deposited at lower temperature could suppress the nucleation at the $Si-SiO_2$ interface while the upper layer deposited at higher temperature could nucleate with a smaller number of nucleation sites. The incubation time and transformation behavior were determined by the deposition temperature of the upper layer. As an example, the grain size of the double layer film deposited sequentially at $150\,^\circ\!C$ and $200\,^\circ\!C$ enhanced to $1.8 \mu m$ while that of the monolayer film deposited at $200\,^\circ\!C$ was $1.4 \mu m$.
