Microcrystalline silicon films were formed on glass substrate at 300 • C using pulse-modulated ultrahigh-frequency plasma, with variation of the pulse duty ratio (10-100%) and the pulse frequency (2-50 kHz). We found that the ratio of (111) to (220) crystalline orientation of films can be precisely controlled by changing the duty ratio or frequency. Variation in crystalline orientation closely correlated with the ratio of silicon atom density to hydrogen atom density in the plasma. Strongly preferential (111) growth was achieved, and we propose that the mechanism for this involves the ratio between silicon species and hydrogen atoms in the pulse-modulated plasma.