Germanium-on-insulator(GOI)is promising material for future integrated circuits due to its higher carrier mobilities and with all of the advantages as SOI for MOSFET[1-2].The short channel effect has turned into one of the critical obstruction to miniaturize MOSFETs,Ultra Thin Body(UTB)MOSFET has become one of the promising structures to overcome this issue compared with conventional bulk MOSFETs[3].Although significant progress has been made in Ge materials and devices,we are still facing some big challenges in making ultra-thin GOI materials and Ge MOSFETs.The passivation of Ge surface to achieve low interface states between high-k dielctrics and Ge channel is still one of the critical issues in the fabrication of Ge MOSFETs[4].In this talk,Ultra-thin GOI was fabricated by modified Ge condensation process of a SiGe on SOI substrate.The prepared GOI was then oxidized in O3 at 400℃ for various times to get a thinner Ge layer.In transmission electron microscopy measurements,the obtained GOI layer exhibited a single-crystal structure and a smooth Ge/SiO2 interface.In order to reduce dark current and interface states between HfO2 and Ge,We passivated Ge surface with germanium oxynitride(GeON)layers formed by NH3 plasma nitridation(1,2 or 5min)at 300℃ with a bias power of 2500w in ALD chamber.The lower interface states were achieved for HfO2/Ge structures after the sampels were annealed at 300℃ for 10min in O3 environment.