The effects of narrow channel width on the threshold voltage of deep submicron silicon-on-insulator (SOI) nMOSFETs with LOCOS isolation have been investigated. The reverse narrow channel effect (RNCE) in SOI devices is found to be dependent on the thickness of the active silicon film. A thinner silicon film is found to depict less threshold voltage fall-off. These results can be explained by a reduced oxide/silicon interface area in the transistor width direction, thus the boron segregation due to silicon interstitials with high recombination rate is reduced.