Channel Stress and Ballistic Performance Advantages of Gate-All-Around FETs and Inserted-Oxide FinFETs

Detailed stress modeling of various three-dimensional (3-D) MOSFET designs reveals that the “inserted-oxide” FinFET and gate-all-around (GAA) stacked-nanowire MOSFET (GAAFET) exhibit increased longitudinal stress and decreased transverse stress in both p-channel and n-channel devices, as compared against the bulk FinFET. By combining 3-D electrostatics modeling with mid-channel Schrödinger-Poisson calculations for transport characteristics, it is projected that these changes in stress profile together with the addition of (100)-oriented channel surfaces in the iFinFET and GAAFET affect the carrier effective mass and therefore injection velocity, enhancing the electron transport, but retarding hole transport. Combining the effect on injection velocity with the effect of improved electrostatic integrity, the GAAFET and iFinFET are each found to have a higher drive current for the same off current, relative to the bulk FinFET, with the iFinFET trading some drive current relative to the GAAFET for a substantially shorter gate stack height and simpler structure. These results suggest the iFinFET is a strong candidate for continued MOSFET scaling.