We report an experimental study of the mobility in TiN/HfO2 gate stacks focused on the accurate determination of the HfO2 remote soft phonon scattering mechanism. The high-kappa intrinsic mechanism is clearly dissociated from Coulomb scattering which generally dominates the mobility degradation in high-kappa/metal gate stacks. The temperature dependence of this additional phonon scattering mechanism is nearly linear. This scattering mechanism is shown to be negligible with a metal gate for a SiOx interfacial layer (IL) thicker than 9-10 angstrom. For an IL thickness of 7 angstrom, this mechanism degrades the electron mobility at high effective fields (1 MV/cm) by similar to 13-16% at 300 K and similar to 10-12% at 400 K. (c) 2006 Elsevier Ltd. All rights reserved.