Hydrogen and water vapor plasma downstream treatment with the downstream injection of NF3 removes native oxide from silicon surfaces. In contact hole cleaning, this dry processing is a promising alternative to HF wet treatment, which has a problem of expansion of hole diameter. We examined the etching characteristics of boron-phosphosilicate glass (B-PSG) films, as a typical oxide material for the side-walls of the contact holes and compared the etching depths of B-PSG and thermal oxide films. We found that the etching depths of B-PSG films fell to one third of those of thermal oxide films at lower treatment temperature. This result indicates that the expansion of contact hole diameters can be minimized.