Optimum Channel Design of Extremely-Thin-Body nMOSFETs Utilizing Anisotropic Valley—Robust to Surface Roughness Scattering

Extremely thin-body (ETB) nanosheet channels are considered as the most promising structure of complementary metal–oxide–semiconductor devices in future technology nodes. However, mobility degradation due to surface roughness scattering is a critical challenge. In this article, we propose that an anisotropic valley with a heavy confinement mass is very robust to surface roughness scattering in ETB channels. Our revised physical model of surface roughness scattering allows us to predict the mobility in ETB channels quantitatively. Our model is in good agreement with the experimental mobility under directly measured roughness parameters. Based on this model, we assessed the optimum ETB channels of (100) Si, (100) and (111) Ge, and (111) InAs down to 2 nm. Simulation results showed that the (111) Ge-on-insulator (GOI) is the most promising because of the strong anisotropy of the L valley and excellent electron mobility even in the 2-nm-thick channels, which is an advantage over Si and 2-D materials.