Practical and controllable etch rates are obtained for chemical-mechanical polishing (CMP)-processed single crystalline langasite (La3Ga5SiO14) wafers in Cl-2/Ar inductively coupled plasmas. The effects of plasma composition, ion flux, and ion energy on the etch rate and surface morphology are examined. A maximum etch rate similar to 1600 angstrom/min was achieved either at relatively high source power (similar to 1000 W) or high Cl-2 content conditions and the etched surfaces are found to retain smooth surface morphology under a wide range of plasma conditions. The CMP-induced subsurface layer formed in the langasite wafer was successfully removed in Cl-2/Ar inductively coupled plasmas and the electrical conductivity was restored to the initial value (similar to 1 X 10(-4) Omega(-1) cm(-1)) measured before being CMP processed at an etch depth of similar to 700 angstrom. (c) 2005 American Vacuum Society.