Microcrystalline silicon films were deposited by a cathode type RF grow discharge system using a small percent of SiH4 diluted with hydrogen. Crystallized Si films were deposited at the power density from 0.4 to 0.8 W cm(-2) and the substrate temperature above 350 degrees C. The effects of RF power and substrate temperature on crystalline structure and the thermal activation energy of the films are investigated. It is found that the crystallinity and electrical properties of films deposited strongly depend on RF power. The crystallization process is suggested to take place due to the steady state between the growth of film and etching of the films by atomic hydrogen radicals.