The aim of this work is to understand the mechanism behind facet formation during epitaxial growth of silicon induced by excimer laser which leads to formation of subgrains in the final crystallized films. We use a phase-field methodology applied to a three-dimensional finite elements simulation of the melt and regrowth phase of silicon during the excimer laser annealing. Due to the specific patterning of the structure, a thermal gradient exists which leads to geometrically non-uniform solidification front. This observation may be the main reason for the generation of subgrains..