Abstract: In the crystal structure of a polysilicon thin film having a field effect mobility .mu..sub.FE of about 80 cm.sup.2 /V.multidot.sec, a grain size is about 200 nm and a crystallite size on the (111) plane is about 180 nm. The crystal size corresponds to the size of a completely monocrystallized portion of a grain. The condition of obtaining a field effect mobility .mu..sub.FE of about 80 cm.sup.2 /V.multidot.sec is that the crystallite size on the (111) plane is at least 180 nm (measured value). By taking the crystallite size into consideration, it becomes possible to achieve a high field effect mobility .mu..sub.FE which cannot be obtained merely by increasing the grain size.

Abstract: A method of preparing a semiconductor device, comprising: forming an amorphous silicon layer on a substrate, and applying shots of an excimer laser beam to the amorphous silicon layer to convert the amorphous silicon layer into a polysilicon layer having a plurality of silicon grains, each of the grains having a grain size and including a crystallite having a crystallite size on the (111) plane, an average value of the crystallite sizes on the (111) plane of the crystallites included in the polysilicon layer being sixty percent or greater of an average value of the grain size.

Abstract: In the crystal structure of a polysilicon thin film having a field effect mobility .mu..sub.FE of about 80 cm.sup.2 /V.sec, a grain size is about 200 nm and a crystallite size on the (111) plane is about 180 nm. The crystal size corresponds to the size of a completely monocrystallized portion of a grain. The condition of obtaining a field effect mobility .mu..sub.FE of about 80 cm.sup.2 /V.sec is that the crystallite size on the (111) plane is at least 180 nm (measured value). By taking the crystallite size into consideration, it becomes possible to achieve a high field effect mobility .mu..sub.FE which cannot be obtained merely by increasing the grain size.