This paper presents an experimental examination of hole mobility in ultra-thin body (UTB) SOI MOSFETs, covering wide ranges of T/sub SOI/ (between /spl sim/3.7 nm and /spl sim/50 nm), and temperature (between /spl sim/79 K and /spl sim/320 K). This paper addresses the observed strong degradation of hole mobility at extremely thin T/sub SOI/, proposing an additional surface roughness scattering mechanism for the thinnest samples due to the perturbation of the conducting band potential stemming from spatial confinement.