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Intrinsic correlation between mobility reduction by remote Coulomb scattering (RCS) and threshold voltage shift (DeltaVt), both of which are induced by interface dipole modulation at high-k/SiO2 interface, is investigated. Three types of dipole modulation are examined; Al addition, La addition, and changing quality of interfacial SiO2 layer. Extrinsic scattering components due to increases of interface state and surface roughness are extracted and separated. It is found that RCS due to interface dipole modulation by Al addition increases with increasing DeltaVt, while that by La addition is constant, independent of DeltaVt. Inevitability of additional scattering for DeltaVt is discussed based on two different models for dipole formation mechanisms.