Ferroelectric YMnO3 thin films are excellent dielectric materials for high integrated ferroelectric random access memory with a metal - ferroelectric-silicon field effect transistor structure. In this study, YMnO3 thin films were etched with Cl-2/Ar gas chemistries in inductively coupled plasma. The maximum etch rate of YMnO3 thin films is 285 Angstrom /min under Cl-2/(Cl-2+Ar) of 1.0, 600 W/-200 V and 15 mTorr. The selectivities of YMnO3 over CeO2 and Y2O3 are 2.85 and 1.72, respectively. The results of x-ray photoelectron spectroscopy (XPS) reflect that Y is removed dominantly by chemical reaction between Y and Cl, while Mn is removed more effectively by Ar ion bombardment than chemical reaction. The results of the secondary ion mass spectrometer were equal to these of XPS. The etch profile of the etched YMnO3 film is approximately 65 degrees and free of residues at the sidewall.