Experimental studies of the etching of (Ba,Sr)TiO3 (BST) have been performed in Ar/halogen and Cl-2 plasmas. In spite of the poor volatility of halogenated barium and strontium, some chemical enhancement of the etching reaction was observed in the etching of BST with halogen-containing plasmas. An investigation of the etching of BaOx, SrOx, TiOx, and BaxSryOz films with Cl-2 plasma showed that the chemical enhancement in BST etching was related to the existence of titanium in BST films. The chemical reactivity of titanium with chlorine seemed to enhance the etching of BST. In the x-ray photoelectron spectroscopy analysis of the BST surfaces etched with Cl-2 plasma, we found that barium- and strontium-rich surfaces were formed during the etching and that etching residues consisting of barium and strontium were observed after the BST films were etched off.