A gate stack structure consisting of a polycrystalline silicon germanium (poly-SiGe) conductor and a HfO2 dielectric on a silicon substrate was formed by inductively coupled plasma etching using HBr/Cl-2/O-2. Etch rates of poly-SiGe with 46% Ge were 1.7-2.0 times higher than those of polycrystalline silicon, depending on processing conditions. In the small feature sized devices of 100 nm gates, the notching at the sidewall of poly-SiGe was pronounced up to the depth of 50 nm. The amount of notching increased with increasing inductive power and pressure, and decreasing rf bias power. A HfO2 etch rate of 950 Angstrom/min was obtained at the condition of 5 50 W inductive power, 360 W rf bias power, and 10 mTorr pressure. Etch rates of HfO2 increased with increasing inductive power and rf bias power. Etching selectivity of poly-SiGe with respect to HfO2 increased significantly with the addition of. 3.8% O-2 to HBr, and it was possible to control the selectivity in the range of 15-70 by changing the rf bias power. The change in etching selectivity was considered mainly due to the change in HfO2 film property, originating from the incorporation of O into the remaining nonvolatile Hf and the reformation,of HfOx during etching. (C) 2003 American Vacuum Society.