A method of forming polycrystalline silicon film with large grains at a controlled location using a single irradiation of an excimer laser beam is proposed. The excimer laser beam is modified to have a specific spatial intensity profile, periodic spatial variation of intensity maxima (I-max) and minima (I-min), by means of a specially designed mask composed of transparent and opaque patterns. It is noted that the evolution of polycrystalline silicon microstructure is critically dependent on the melt depth of amorphous silicon at Imin, which we categorized as "partial melting," " near-complete melting," and "complete melting" regimes. While the lateral grain growth of polycrystalline silicon increases in proportion to the fluence gradient as the energy density is increased, surprisingly we find that it decreases in the complete melting regime due to the "secondary nucleation" occurring at Imax. By judicious selection of optimum intensity modulation and the spacing between Imax and Imin, we have obtained the maximum lateral grain size of 7.0 mu m at controlled position. (c) 2007 The Electrochemical Society.