Ultrathin gate oxide CMOS with nondoped selective epitaxial Si channel layer

The nondoped selective epitaxial Si channel technique has been applied to u ltrathin gate oxide CMOS transistors. It was confirmed that drain current d rive and transconductance are improved in the epitaxial channel MOSFETs wit h ultrathin gate oxides in the direct-tunneling regime, It was also found t hat the epitaxial Si channel noticeably reduces the direct-tunneling gate l eakage current, The relation between channel impurity concentration and dir ect-tunneling gate leakage current was investigated in detail. It was confi rmed that the lower leakage current in epitaxial channel devices was not co mpletely explained by the lower impurity concentration at the channel, The results suggest that the improved leakage current in the epitaxial channel case is attributable to the improvement of some aspect of the oxide film qu ality, such as roughness or defect density, and that the improvement of the oxide film quality is essential for ultrathin gate oxide CMOS, AFM and 1/f noise results support that SiO2/Si interface quality in epitaxial Si chann el MOSFETs is improved. Good performance and lower leakage current of TiN g ate electrode CMOS was also demonstrated.