We report the successful electron-beam patterning of Ge2Sb2Te5 nanostructures, in the form of both lines and dots, using hydrogen silsesquioxane ( HSQ ) resist. Although HSQ has proven to be a good resolution electron-beam resist, the adhesion between Ge2Sb2Te5 and the HSQ resist is problematic when trying to form fine patterns. To promote their adhesion, we introduced an amorphous Si ( a-Si ) layer between the Ge2Sb2Te5 and HSQ layers, and the layers were then sequentially removed using Cl-2 reactive ion etching and Ar etching with good selectivity of each layer. The selectivities for HSQ: a- Si etched by Cl-2 reactive gas and a-Si: Ge2Sb2Te5 etched by Ar gas were 1: 2.7 and 1: 17, respectively. On the basis of this multilayer structure and a two-step dry etching process, various Ge2Sb2Te5 nanostructures as small as 40 nm were successfully fabricated. (c) 2007 The Electrochemical Society.