SiO@sub 2@ etching is done by using fluorocarbon gases to deposit a fluoropolymer on the underlying silicon. This deposit enhances the etching selectivity of SiO2 over silicon or silicon nitride. CF@sub 2@ radicals especially are used as the main gas precursor for polymer deposition. In a conventional gas plasma, however, the CF@sub 2@ radicals and other radicals (high-molecular-weight-radicals: C@sub x@F@sub y@) lead to the polymerization. This condition causes microloading and etching-stop in high-aspect-contact hole patterning due to the sidewall polymerization during SiO@sub 2@ etching processes. Conversely, by new fluorocarbon gas chemistries (C@sub 2@F@sub 4@/CF@sub 3@I), we achieved selective radical generation of CF2 and eliminated high-molecular-weight-radicals. Under this condition, microloading-free and etching-stop-free high-aspect-ratio-contact-holes patterning of SiO@sub 2@ was accomplished. Thus, the higher molecular weight radicals play an important role in the sidewall polymerization in contact holes because these radicals have a higher sticking coefficient than CF@sub 2@ radicals. Selective generation of CF@sub 2@ radicals and suppression of C@sub x@F@sub y@ radicals are thus necessary to eliminate the microloading and etching-stop when formation high-aspect-contact-ratio holes.