It is an object of the present invention to align the plane orientations of crystal grains of a semiconductor film crystallized by irradiation with a linear laser beam with a width of less than or equal to 5 μm. By performing irradiation with the linear laser beam condensed by an aspheric cylindrical lens or a gradient index lens to completely melt the semiconductor film and scanning the linear laser beam, the completely melted semiconductor film is made to grow laterally. Because the linear beam is very narrow, the width of the semiconductor which is in a liquid state is also narrow, so the occurrence of turbulent flow in the liquid semiconductor is suppressed. Therefore, growth directions of adjacent crystal grains do not become disordered due to turbulent flow and are unformalized, and thus the plane orientations of the laterally grown crystal grains can be aligned.