An appreciable mobility enhancement up to 35% is found in p-channel MOSFETs with a stramed-Si0.7Ge0.3 surface-channel under an ALD TiN/Al2O3/HfAlOchi/Al2O3 gate stack, as compared to a Si-channel reference transistor under an identical gate stack. A distorted effective mobility curve with a slow mobility roll-off at low vertical electric field is however extracted for the Si0.7Ge0.3 devices following the standard split-CV measurement procedure. A high density of interface traps on the order of 10(12) cm(-2) eV(-1) is found in these Si0.7Ge0.3 devices using charge-pumping measurements. Thus, this distortion is attributed partly to trapping of a significant fraction of the inversion carriers at the interface between the high-kappa dielectrics and the Si0.7Ge0.3 channel, thus defeating the validity of the usual formulation for mobility extraction. By taking into account the trapped carriers that are detectable by the split-CV measurement but do not contribute to the drain conductance, a corrected effective mobility curve is obtained. The distortion of the effective mobility curve is nonetheless mainly due to mobility degradation as a result of Coulomb scattering of the mobile channel carriers by the charged interface defects, i.e. charged traps or trapped carriers that remain charged. (C) 2003 Elsevier Ltd. All rights reserved.