Abstract: An object is to provide a power storage device provided with a battery that is a power storage means, for safe and accurate supply of electric power in a short period of time for drive power supply voltage without checking remaining capacity of the battery or changing batteries with deterioration over time of the battery for drive power supply voltage. The power storage device is provided with a battery that is a power storage means as a power supply for supplying electric power and a counter circuit for counting charging time of the power storage means. An electromagnetic wave with electric field intensity, magnetic field intensity, and power flux density per unit time which are transmitted from a power feeder are controlled, and the power storage means is efficiently charged using the electromagnetic wave in a short period of time.

Abstract: A semiconductor device having a display unit, which is small in size, suppresses the defect caused by the mounting of IC chips and the like on the substrate, and operates at a high speed. A semiconductor display unit and other circuit blocks are integrally formed on the substrate having an insulating surface by using a process for fabricating TFTs that realize a high degree of mobility. Concretely, there is employed a process for crystallizing a semiconductor active layer by using a continuously oscillating laser. Further, the process for crystallization relying upon the continuously oscillating laser is selectively effected for only those circuit blocks that must be operated at high speeds, thereby to realize a high production efficiency.