The etching properties of Si(100) and (111) substrates by H-2 and Ar plasmas excited by the ECR technique were investigated. The Si(100) substrate is more easily etched than the Si(111) substrate. This is explained by the difference of the bonding formation of surface Si atoms. The Si film structure deposited on a glass substrate was characterized to be an amorphous/polycrystalline bilayer structure. A 30-40-nm thick amorphous Si layer first grew, followed by a (110) preferentially oriented poly Si layer. Low temperature epitaxial growth properties of Si films obtained using the ECR plasma CVD technique were investigated. The crystallinity of Si films deposited on a Si(100) substrate was influenced by the H-2 flow rate. The mechanism of epitaxial growth is explained by the selective etching model of the amorphous region at temperatures below 300 degreesC.