To provide a semiconductor device, which is capable of supplying a stable voltage to a memory and communicating wirelessly in writing data into a memory, and a driving method thereof. The semiconductor device is operated with periods which are divided into a period for receiving a signal wirelessly from a reader/writer, and a period for boosting up electric power received wirelessly from the reader/writer before being supplied to the memory. The signals transmitted from the reader/writer include timing for completion of signal transmission as information. The timing for completion of signal transmission is known by receiving the signals. After completion of signal transmission from the reader/writer, electric power received from the reader/writer starts to be boosted up, and then it is supplied to the memory in the semiconductor device.