We have studied the new dry etching using a multiply-charged ion beam of which potential energy increases with its charge state, and multiply-charged ion has a high potential energy than a single charged ion. This paper proposes a new dry etching of semiconductor materials using the potential energy of the multiply-charged ion beam. When the multiply-charged Ar ions irradiate GaAs surface, not only the physical sputtering in vacuum but also the ion-induced chemical etching in Cl 2 ambient is enhanced. This enhancement is found to be remarkable at the high potential energy region with a higher charge state.