Power consumption of a semiconductor device is reduced by sharpening the rise of a drain current when a gate voltage of a field effect transistor is less than a threshold voltage. As means therefor, in a fully-depleted MOSFET in which a thickness of a semiconductor layer serving as a channel region is 20 nm or less, a gate plug connected to a gate electrode is constituted of a first plug, a ferroelectric film, and a second plug sequentially stacked on the gate electrode. Here, an area where a contact surface between the first plug and the ferroelectric film and a contact surface between the ferroelectric film and the second plug overlap in a plan view is smaller than an area where the gate electrode and a semiconductor layer serving as an active region overlap.