Semiconductor device and method for manufacturing the same

摘要

An object is to provide a high reliable semiconductor device including a thin film transistor having stable electric characteristics. In a method for manufacturing a semiconductor device including a thin film transistor in which an oxide semiconductor film is used for a semiconductor layer including a channel formation region, heat treatment (which is for dehydration or dehydrogenation) is performed so as to improve the purity of the oxide semiconductor film and reduce impurities such as moisture. Besides impurities such as moisture existing in the oxide semiconductor film, heat treatment causes reduction of impurities such as moisture existing in the gate insulating layer and those in interfaces between the oxide semiconductor film and films which are provided over and below the oxide semiconductor film and are in contact with the oxide semiconductor film.

主权项

1. A method for manufacturing a semiconductor device comprising the steps of:
forming an oxide semiconductor layer over an insulating layer; heating the oxide semiconductor layer under an inert atmosphere at a temperature equal to or higher than 450° C., whereby a carrier concentration in the oxide semiconductor layer is equal to or higher than 1×1018 cm−3; and forming an oxide insulating layer over and in contact with a part of the oxide semiconductor layer, whereby a carrier concentration in the part of the oxide semiconductor layer is lower than 1×1018 cm−3, wherein a hydrogen concentration in the oxide semiconductor layer is lower than 3×1020 cm−3.