Etching behaviors of (Ba,Sr)TiO3 (BST) thin films were studied by an inductively coupled plasma (ICP). Using Cl-2 gas with Ar gas, etch rate of the BST thin films and their selectivity for SiO2 hard masks were systematically investigated over a wide range of gas mixing ratio and ICP power. The films were etched at rates of 400 Angstrom/min using 20% of Cl-2 flow and 80% of Ar flow under ambient pressure below 10 mTorr and at a reactive ion etch power of 150 W and at an ICP power of 700 W. Chemical analysis by Auger electron spectroscopy showed that postetch residues had Ba- and Sr-rich phases which were not found on the surface of the SiO2 hard mask. It was found that the residues of the BST films can be removed with the addition of SF6 gas in the etchant gas mixture.