A carrier-mobility model for high-k gate-dielectric Ge MOSFETs with metal gate electrode

A mobility model for high-k gate-dielectric Ge pMOSFET with metal gate electrode is proposed by considering the scattering of channel carriers by surface-optical phonons in the high-k gate dielectric. The effects of structural and physical parameters (e.g. gate dielectric thickness, electron density, effective electron mass and permittivity of gate electrode) on the carrier mobility are investigated. The carrier mobility of Ge pMOSFET with metal gate electrode is compared to that with poly-Si gate electrode. It is theoretically shown that the carrier mobility can be largely enhanced when poly-Si gate electrode is replaced by metal gate electrode. This is because metal gate electrode plays a significant role in screening the coupling between the optical phonons in the high-k gate dielectric and the charge carriers in the conduction channel.