  We report on the hole mobility of ultra-narrow [110] Si channels as a
function of the confinement length scale. We employing atomistic bandstructure
calculations and linearized Boltzmann transport approach. The phonon-limited
mobility of holes in thin [110] channels can be improved by more than 3X as the
thickness of the (110) confining surface is reduced down to 3nm. This behavior
originates from confinement induced bandstructure changes that decrease the
hole effective mass and the scattering rates. Our results provide explanations
for recent mobility measurements in nanobelts of similar dimensions.
