1.  Field of the Invention
The present invention relates to a plasma CVD method used for manufacturing a semiconductor integrated circuit such as a thin-film transistor. 
2.  Description of the Related Art
At the present time, as the semiconductor integrated circuit is made high in integration as well as density, there is advanced that the structure of a semiconductor element is made finer.  Under this condition, there is such a demand that an interlayer insulating film not only has an insulating characteristic, but also can be filled closely between wires which are complicated and have high aspects.  Up to now, since a silicon oxide film which is made of TEOS as raw material and formed through the CVD method is excellent in coating shape, it has been widely used as an interlayer insulating film.  In particular, the plasma CVD method is applied since it enables the silicon oxide film to be manufactured at a low temperature of 400° C. or lower and also enables a large area to be processed, in a process of manufacturing a TFT which is to be formed on a glass substrate. 
However, as the semiconductor integrated circuit is made high in integration as well as density, the influence of charge-up of electrons caused during a plasma process becomes remarkable.  For example, it is presumed that the failure of U-shaped display and the defect of points are caused by electric damages during the process.  In the active matrix type liquid-crystal display unit, the failure of one TFT means the failure of an entire panel, thereby leading to the deterioration of a yield.