Semiconductor device and manufacturing method thereof

摘要

A threshold voltage of a thin film transistor is adjusted. The thin film transistor is manufactured through the steps of: introducing a semiconductor material gas into a treatment chamber; forming a semiconductor film in the treatment chamber over a gate insulating layer provided covering a gate electrode; evacuating the semiconductor material gas in the treatment chamber; introducing rare gas into the treatment chamber; performing plasma treatment on the semiconductor film in the treatment chamber; forming an impurity semiconductor film over the semiconductor film; processing the semiconductor film and the impurity semiconductor film into island shapes, so that a semiconductor stack is formed; forming source and drain electrodes in contact with an impurity semiconductor layer included in the semiconductor stack. Argon is preferably used as the rare gas. The rare gas element is preferably contained in the semiconductor film at 2.5×1018 cm-3 or more.