| abstract |
A transistor having high electrical characteristics even with a fine structure is provided with high yield. A semiconductor device including the transistor also achieves high performance, high reliability, and high production. In a semiconductor device including a transistor in which an oxide semiconductor layer, a gate insulating layer, and a gate electrode layer provided with a sidewall insulating layer on a side surface are sequentially stacked, the source electrode layer and the drain electrode layer are formed of an oxide semiconductor. The layer and the sidewall insulating layer are provided in contact with each other. In the manufacturing process of the semiconductor device, a conductive layer and an interlayer insulating layer are stacked so as to cover the oxide semiconductor layer, the sidewall insulating layer, and the gate electrode layer, and the interlayer insulating layer on the gate electrode layer is formed by a chemical mechanical polishing method. Then, the conductive layer is removed to form a source electrode layer and a drain electrode layer. Before the gate insulating layer is formed, a cleaning process is performed on the oxide semiconductor layer. [Selection] Figure 1 |