US Patent 11967557 Semiconductor device and manufacturing method thereof

A semiconductor device includes a substrate. A gate insulating film is formed on the surface of the substrate. A first gate electrode layer is formed on the gate insulating film. A second gate electrode layer is formed on the first gate electrode layer and electrically connected to the first gate electrode layer. A first contact extends through the second gate electrode layer to reach the first gate electrode layer. First and second impurity layers are formed on opposite sides of the first and second gate electrode layers.