N-2 and NO gas addition to F-2/Ar remote plasmas during chemical dry etching (CDE) of low-k SiOCH layer was effective in increasing the etch rate, but the addition of O-2 decreased the etch rate. And, the injection of NO gas directly into the reactor increased the SiOCH etch rate most significantly. The addition of N-2 or NO gas contributes to an effective removal of oxygen in the SiOCH layer, by forming NO2 and HNO3 by-products, and of carbon species in the SiOCH layer by forming CF4 by-product, which leads to enhancement of SiF4 formation and in turn increase in the SiOCH etch rate. (C) 2007 Elsevier B.V. All rights reserved.