Interface-controlled self-align source/drain Ge pMOSFETs using thermally-oxidized GeO2 interfacial layers

We have found that GeO₂/Ge MOS structures fabricated by direct thermal oxidation yield significantly low interface trap density (D_it). Thus, Ge pMOSFETs using the GeO₂/Ge MOS structures with the superior interface properties have been fabricated for achieving high hole mobility and investigated for examining the impact of the interface properties on the device performance. Al₂O₃ or SiO films were employed for protecting the GeO₂/Ge MOS structures during the FET fabrication processes. The relationship between mobility and the fabrication conditions, such as the oxidation temperature, the annealing gas species, the substrate impurity concentration, the thickness of Al₂O₃ cap, and the surface orientation have been clarified.