Gate-first Germanium nMOSFET with CVD HfO₂ gate dielectric and silicon surface passivation

A gate-first self-aligned Ge n-channel MOSFET (nMOSFET) with chemical vapor deposited (CVD) high-κ gate dielectric HfO₂ was demonstrated. By tuning the thickness of the ultrathin silicon-passivation layer on top of the germanium, it is found that increasing the silicon thickness helps to reduce the hysteresis, fixed charge in the gate dielectric, and interface trap density at the oxide/semiconductor interface. About 61% improvement in peak electron mobility of the Ge nMOSFET with a thick silicon-passivation layer over the CVD HfO₂/Si system was achieved.