  In this letter, we report a three-dimensional (3D) quantum mechanical
simulation to investigate the effects of surface roughness scattering (SRS) on
the device characteristics of Si nanowire transistors (SNWTs). We treat the
microscopic structure of the Si/SiO2 interface roughness directly by using a 3D
finite element technique. The results show that 1) SRS reduces the electron
density of states in the channel, which increases the SNWT threshold voltage,
and 2) the SRS in SNWTs becomes more effective when more propagating modes are
occupied, which implies that SRS is more important in planar
metal-oxide-semiconductor field-effect-transistors with many transverse modes
occupied than in small-diameter SNWTs with few modes conducting.
