| abstract |
A transistor with excellent electrical characteristics is provided. A substrate having an insulating surface is prepared, a stacked film including a first oxide semiconductor layer and a second oxide semiconductor layer is formed over the substrate, and a mask layer is formed over part of the stacked film. After forming the film, dry etching is performed to remove the laminated film leaving the region where the mask layer is provided, and after forming the reaction product on the side surface of the remaining laminated film and removing the mask layer The reaction product is removed by wet etching, a source electrode and a drain electrode are formed on the stacked film, and a third oxide semiconductor layer, a gate insulating film, and a gate electrode are formed on the stacked film, the source electrode, and the drain electrode. The gate electrodes are sequentially stacked. [Selection] Figure 1 |