The etching characteristics of Ge2Sb2Te5 (GST) films were studied with a CHF3/O-2 gas mixture using a reactive ion etching system. The variations of etch rates and etch profiles caused by changes in the gas-mixing ratio were investigated under constant pressure and applying power. Then the etching parameters were optimized. The etch rate is up to 83 nm/min, and the selectivity of GST to SiO2 is as high as 3 times. The smooth surface was achieved using optimized etching parameters of oxygen concentration of 4% in the CHF3/O-2 gas mixture, pressure of 30 mTorr, and power of 150 W. (c) 2007 The Electrochemical Society.