We report a simple theoretical model based on experimental data about the interface roughness effect between gate oxide and metal gate on dielectric. From the analytic approach, we confirm that the increase in interface roughness generates the decrease in the dielectric constant as well as the increase in the leakage current. We checked the interface roughness effect between high-kappa HfO(2) gate oxides and Ru gates by atomic layer deposition (ALD) and physical vapor deposition (PVD). The ALD Ru gate showed better dielectric properties (high dielectric constant and low leakage current) and lower interface roughness than the PVD Ru metal gate. (C) 2009 Elsevier B.V. All rights reserved.