The etch characteristics of iridium ruthenium (IrRu) thin films with titanium nitride (TiN) hard mask were studied by varying the etch gas concentration in a high density inductively coupled plasma. Firstly, TiN hard mask was etched using Cl2/C2F6/Ar mixture. The etch rates and etch profiles of IrRu films were investigated as a function of O2 gas concentration in O2/Cl2/Ar mixture. Etch rates were measured by dektak surface profilometer, and etch profiles were observed by field emission scanning electron microscope. A residue-free IrRu etching with a sidewall angle of approximately 70°-75° was obtained at the optimal etch conditions.