Combined with atomic force microscope (AFM), micro-Raman spectroscope, cross-section transmission electron microscope (TEM) and high resolution electron microscope (HREM) analyses, the surface morphology and structures of a-Si:H/a-SiNx,:H multilayers (MLs), irradiated by excimer laser through the phase shifting mask grating, are investigated. It is found that Si nanocrystallites (nc-Si) are formed within the initial a-Si:H sublayers, and the size of the grains can be controlled due to the constrained crystallization effect. And it is possible to use this laser interference crystallization (LIC) method to get the periodic distribution of nc-Si in both transverse and longitudinal direction.