Strain-induced enhancement of carrier mobility is essential for achieving high-speed transistors. The effects of thermal-annealing (temperature: 400-1150 degrees C) and ultraviolet (UV) laser-annealing (wavelength: 248 nm, temperature: 30-400 degrees C) on strain-enhancement in Si-pillars covered with Si3N4 stress-liners by plasma-enhanced chemical vapor deposition are investigated. Before annealing, the Si3N4 stress-liners induce a tensile strain (similar to 0.5%) in Si. After thermal-annealing (>800 degrees C), the strain becomes highly compressive (>similar to 0.4%), because of dehydrogenation-induced structural relaxation in Si3N4 films. On the other hand, the tensile strain becomes large (>similar to 0.7%) after UV laser-annealing at 400 degrees C, due to non-equilibrium dehydrogenation in Si3N4 films. This strain-enhancement technique is useful for the realization of advanced high-speed three-dimensional transistors. (C) 2011 Elsevier B. V. All rights reserved.