DC reactive sputtering on a Si-O-2/Ar system was studied for stable SiO2 film formation with high deposition rates. The applied voltage to the cathode was modulated periodically with positive pulses, and the arcing problem was solved. The plasma observation using a high-speed camera revealed that the plasma emission almost disappeared during the positive pulse when it was applied for even 5 mu s and the emission intensity changed according to the current supplied through the Si target. The current versus voltage curves obtained during the sputtering period (the I-V curves) are continuous and the system has no avalanche-like state jump between the oxide mode and the metal mode (unpoisoned mode). High-rate deposition of the SiO2 was consequently achieved in the transition mode without a feedback system.