An SiO2 contact hole with a diameter of 0.17 mum and an aspect ratio of 15 was etched in C4F6/O-2/Ar and C4F6/O-2/Ar/CH2F2 plasmas, and the effects of CH2F2 gas on the etch profiles and the etch selectivity to photoresist were investigated. The addition of CH2F2 gas enhanced the production of fluorocarbon films by reactive C-F species, resulting in more fluorocarbon films deposited on the photoresist layer and the sidewalls of the contact hole compared to the CH2F2 gas being absent. This finally led to drastic improvements in the critical dimension loss and the etched contact profiles. The etch selectivity to photoresist was also enhanced in the presence of CH2F2 gas due to hydrogen atoms as well as reactive C-F species. X-ray photoelectron spectroscopy analyses showed that the fluorocarbon films produced in the C4F6/O-2/Ar/CH2F2 plasma were more carbon-rich compared to those in the C4F6/O-2/Ar plasma. (C) 2003 The Electrochemical Society.