Method for manufacturing an oxide-based semiconductor thin film transistor (TFT) including out diffusing hydrogen or moisture from the oxide semiconductor layer into an adjacent insulating layer which contains a halogen element

摘要

An object is to provide a semiconductor device with stable electric characteristics in which an oxide semiconductor is used. An impurity such as hydrogen or moisture (e.g., a hydrogen atom or a compound containing a hydrogen atom such as H₂O) is eliminated from an oxide semiconductor layer with use of a halogen element typified by fluorine or chlorine, so that the impurity concentration in the oxide semiconductor layer is reduced. A gate insulating layer and/or an insulating layer provided in contact with the oxide semiconductor layer can be formed to contain a halogen element. In addition, a halogen element may be attached to the oxide semiconductor layer through plasma treatment under an atmosphere of a gas containing a halogen element.