Silicon dioxide film was deposited on Si substrate by plasma-enhanced chemical vapor deposition using a monopole antenna plasma source. Electron density was measured by a plasma absorption probe with and without a grounded plate close to monopole antennas. A high electron density was obtained with the grounded plate. The typical electron density of the monopole antenna plasma source was similar to 3 x 10(10) cm(-3) at a position of 13 mm away from the antenna in oxygen plasma. The electron density rapidly decreased along the distance from the monopole antenna. Since the deposition rate and breakdown field were improved with the higher electron density, the grounded plate improved the performance of the SiO2 film deposition. (c) 2007 Elsevier B.V. All rights reserved.