In this thesis, a study on the characteristics of polycrystalline-silicon (poly-Si) thin films crystallized using near-ultraviolet laser annealing (NULA), green laser annealing (GLA), and blue laser diode annealing (BLDA) was conducted using thermal simulations and non-destructive analyses. A 355-nm pulsed diode-pumped solid-state (DPSS) laser, a 532-nm pulsed DPSS laser, and 450-nm continuous-wave (CW) laser diodes were employed for NULA, GLA, and BLDA, respectively. For a 100-nm-thick amorphous silicon (a-Si) thin film on a SiO₂/Si substrate, three-dimensional heat transfer simulations were performed, and the temperature distributions in the scanning and depth directions were obtained with the variation in the laser power. Based on the thermal simulation results, the optimum power condition was obtained for laser annealing process, and annealing experiments using NULA, GLA, BLDA were conducted. Subsequently, the annealed samples were characterized using Raman spectroscopy, spectroscopic ellipsometry, and atomic force microscopy (AFM). It showed that both the crystal quality and roughness of the annealed film increased as the laser power was increased. In addition, GLA and BLDA resulted in good crystallinity comparable to the results of furnace annealing, whereas NULA resulted in a relatively poor crystal quality. This analytic trend was also consistent with the thermal simulation results. Based on the simulation and characterization results, the optimum laser sources and power levels can be determined for a given a-Si thickness. The demonstrated laser annealing characteristics are expected to provide an insight into the optimum laser annealing conditions to realize high-quality poly-Si.