A ferroelectric capacitor has a top electrode, a bottom electrode, a ferroelectric body disposed between the top and bottom electrodes, and a dielectric lining disposed below the top electrode and above the bottom electrode, protecting the sides of the ferroelectric body. The mobile communications device is operated by a device user. The source electrode is electrically continuously provided across the plurality of unit elements outside the gate electrodes on the first surface and has narrow parts between the gate electrodes which are spaced apart from each other and which belong to adjacent unit elements among the plurality of unit elements. Once the desired shape is achieved, the valve is closed, sealing the bladder.