Elevated field insulator (ELFIN) process for device isolation of ultrathin SOI MOSFETs with top silicon film less than 20 nm

New device isolation process, called elevated field insulator (ELFIN) process, for ultrathin SOI devices with top silicon film less than 20 nm has been proposed and successfully demonstrated. In ELFIN process, gate oxidation and subsequent gate poly-Si deposition is followed by conventional STI process. ELFIN process has a field region elevated compared with active silicon region, leading to prevention of silicon edge from being wrapped around by gate poly-Si. It is found that thin-film SOI NMOSFETs with ELFIN process have better reverse narrow channel effect about 50% at W-G = 0.3 mum than that with conventional shallow trench isolation (STI) process.