Present status of the application of fluidized bed CVD process to poly-Si production from monosilane is reviewed. The advantages of the fluidized bed process have been pointed out so far, it, however, has various problems; undesirable reaction of fines formation, clogging of particles, contamination, and residue hydrogen. From the view points shown above, our experimental studies of fluidized bed CVD of silicon from monosilane, kinetic studies on monosilane pyrolysis and numerical studies on development of fluidized bed reactor model are reviewed. Various properties of the produce silicon are also described. Lastly, our new trials to produce functional materials using monosilane pyrolysis are introduced.