High-performance CESL strained nMOSFET with HfO 2 gate dielectrics has been successfully demonstrated in this work. It is found that, the transconductance (g m ) and driving current (I on ) of the nMOSFETs increase 70% and 90%, respectively, of the increase of devices with a 300 nm capping nitride layer. A superior HfO 2 /Si interface for CESL-devices is observed, demonstrated by an obvious interface state density reduction (6.56×10 11 to 9.85×10 10 cm -2 ). Further, a roughly 50% and 60% increase of g m and I on , respectively, can be achieved for the 300 nm SiN-capped HfO 2 nMOSFET without considering charge trapping under pulsed-IV measurement.