Abstract: A method is disclosed for the production of polycrystalline silicon thin films characterized by performing heat treatment of amorphous silicon thin films deposited on a substrate at a relatively low temperature of between 300.degree. and 600.degree. C. under a pressure ranging from 10.sup.-3 to 1 torr. The method can provide polycrystalline silicon thin films having increased grain sizes of about 60-300 .mu.m. In accordance with the method, glass or ceramic substrates can be used instead of an expensive quartz substrate. SiH.sub.4 gas can also be used instead of Si.sub.2 H.sub.6 gas as a source gas. The polycrystalline silicon thin films disclosed have an electron and positive hole mobility closer to that of the level of single crystals, and thus the development of the SOI element having high performance such as TFT for LCD, or TFT for SRAM, and the like may be greatly advanced.