Semiconductor device having an oxide semiconductor layer

摘要

The reliability of a semiconductor device is increased by suppression of a variation in electric characteristics of a transistor as much as possible. As a cause of a variation in electric characteristics of a transistor including an oxide semiconductor, the concentration of hydrogen in the oxide semiconductor, the density of oxygen vacancies in the oxide semiconductor, or the like can be given. A source electrode and a drain electrode are formed using a conductive material which is easily bonded to oxygen. A channel formation region is formed using an oxide layer formed by a sputtering method or the like under an atmosphere containing oxygen. Thus, the concentration of hydrogen in a stack, in particular, the concentration of hydrogen in a channel formation region can be reduced.

主权项

1. A semiconductor device comprising:
an oxide semiconductor layer including a channel formation region; a first source electrode and a first drain electrode over and in contact with the oxide semiconductor layer; a second source electrode over and in contact with the first source electrode and the oxide semiconductor layer; a second drain electrode over and in contact with the first drain electrode and the oxide semiconductor layer; a first insulating layer over the second source electrode, the second drain electrode and the oxide semiconductor layer; a gate electrode over the first insulating layer; and a second insulating layer over the gate electrode wherein the gate electrode comprises a first layer and a second layer over the first layer, wherein the first layer of the gate electrode is able to reduce a concentration of hydrogen in the channel formation region, wherein the second source electrode and the second drain electrode each comprise a material layer which is able to reduce the concentration of hydrogen in the channel formation region, and wherein a length of the channel formation region is shorter than a distance between the first source electrode and the first drain electrode.