The effects of hot H2O-vapor annealing were investigated on local carrier transport properties over a few grain boundaries in polycrystalline silicon. It shows that hot H2O-vapor annealing effectively reduces grain-boundary dangling bonds and the potential barrier height. In addition, it narrows the distribution of the barrier height value significantly. These effects are thought to originate from oxidation in the vicinity of the film surface, and from hydrogenation in the deeper region. Our results suggest that H2O annealing can improve the carrier transport properties by opening up shorter percolation paths and by increasing the effective carrier mobility and density. (C) 2003 American Vacuum Society.