An object is to alleviate the concentration of an electric field in a semiconductor device. A gate electrode and a drain electrode are provided not to overlap with each other, and an electric-field control electrode is provided between the gate electrode and the drain electrode over a top surface. Insulating layers are provided between the gate electrode and a semiconductor layer and between the electric-field control electrode and the semiconductor layer, and the insulating layer provided between the electric-field control electrode and the semiconductor layer has a larger thickness than the insulating layer provided between the gate electrode and the semiconductor layer. Further, when the semiconductor device is driven, the potential of the electric-field control electrode may be higher than or equal to a source potential and lower than a gate potential, and for example, connection between the electric-field control electrode and the source potential enables such a structure.