| abstract |
In the transistor including the oxide semiconductor film, a metal oxide film is formed for preventing charging that contacts the oxide semiconductor film and covers the source electrode and the drain electrode. Thereafter, oxygen is introduced (added) into the oxide semiconductor film through the metal oxide film and heat treatment is performed. Through these steps of oxygen introduction and heat treatment, impurities such as hydrogen, moisture, hydroxyl groups, or hydrides are intentionally removed from the oxide semiconductor film, and the oxide semiconductor film is highly purified. In addition, by providing the metal oxide film, generation of a parasitic channel on the back channel side of the oxide semiconductor film can be prevented in the transistor. |