Method for manufacturing semiconductor device

摘要

To provide a transistor in which a channel is formed in an oxide semiconductor and which has stable electrical characteristics. To suppress shift in threshold voltage of a transistor in which a channel is formed in an oxide semiconductor. To provide a normally-off switching element having a positive threshold voltage as an n-channel transistor in which a channel is formed in an oxide semiconductor. A base insulating layer is formed over a substrate, an oxide semiconductor layer is formed over the base insulating layer, a first gate insulating layer is formed over the oxide semiconductor layer, a second gate insulating layer is formed over the first gate insulating layer by a sputtering method or an atomic layer deposition method at a substrate temperature of higher than or equal to 100° C., and a gate electrode layer is formed over the second gate insulating layer.

主权项

1. A method for manufacturing a semiconductor device, comprising the steps of:
forming an insulating layer over a substrate; forming an oxide semiconductor layer over the insulating layer; forming a first gate insulating layer over the oxide semiconductor layer; forming a second gate insulating layer over the first gate insulating layer by a sputtering method or an atomic layer deposition method at a substrate temperature of higher than or equal to 100° C.; and forming a gate electrode layer over the second gate insulating layer, wherein the second gate insulating layer includes charge trap states trapping negative charges, and wherein a density of the charge trap states is lower in the first gate insulating layer than in the second gate insulating layer.