| abstract |
A novel manufacturing method for a field effect transistor is provided. Before an amorphous oxide layer is formed on a substrate, the substrate surface is irradiated with ultraviolet rays in an ozone atmosphere, the substrate surface is irradiated with plasma, or the substrate surface is exposed to hydrogen peroxide. Wash with chemical solution. Alternatively, the step of forming an active layer including an amorphous oxide is performed in an atmosphere including at least one of ozone gas and nitrogen oxide gas. Alternatively, the method includes a step of performing heat treatment at a temperature higher than the deposition temperature of the amorphous oxide layer after the amorphous oxide layer is formed over the substrate. [Selection figure] None |