POLYCRYSTALLINE SILICON THIN FILM AND TRANSISTOR USING THE SAME

A polycrystalline silicon thin film with large crystal grain size is formed on a substrate other than single crystalline silicon, e.g. on a glass substrate with low strain point, by plasma CVD or photo CVD. As film-forming gas, a silicon hydride, e.g. Si2 H6 or Si3 H8 is used, and as etchant gas e.g. SiF4 Si2 F6, SiCl4. F2 or Cl, in appropriate mixture; a proportion of a hydrogen-supplying gas may be used. A dopant gas of a Group III or V element can be used to convert the film to an n- or p-type semiconductor. The film formed has a high (100) orientation of 70% or more and a low (220) orientation of less than 30%, a low hydrogen content and fluorine content, and large crystal grain size. It has excellent flatness and is suitable for microstructure fabrication manufacture of thin film transistor. On the film (2) on substrate (1) there can be formed by sputtering source and drain electrodes (3,4), a gate-insulating film (5) and gate electrode (6) to make a thin film transistor device useful e.g. in a liquid crystal display.