Asymmetry in gate capacitance-voltage (C-V) behavior of ultrathin metal gate MOSFETs with Hf[O.sub.2] gate dielectrics

Anomalous asymmetry between accumulation and strong inversion is observed in the measured capacitance-voltage (C-V) curves of metal gate nMOSFETs with Hf[O.sub.2] layers and it is analyzed and extrapolated to still smaller devices and to pMOS devices by using self-consistent Poisson-Schrodinger simulations. The simulations have suggested two mechanisms that result in greater capacitance when the quantum-confined surface carriers are electrons than when they are holes.