The fabrication of nanostructures using self-organized niobium oxide nanopillars was investigated by high-density plasma reactive ion etching in a Cl-2/Ar gas. Etch rates and etch profiles of niobium oxide pillars were examined by varying etch parameters. We confirmed that several nanostructures, such as nanotip and nanodot arrays, could be fabricated over large areas using optimal anodizing and etching conditions. The mechanism of forming different nanostructures were classified into two groups, isotropic and anisotropic etch mechanisms. It is expected that a novel technique proposed in this study offers a simple and cost-effective method for fabricating nanostructures from various material systems. (c) 2005 The Electrochemical Society. All rights reserved.