Abstract: A modulation circuit includes a load and a transistor serving as a switch. The transistor has an oxide semiconductor layer in which hydrogen concentration is 5×1019/cm3 or less. The off-state current of the transistor is 1×10?13 A or less. A modulation circuit includes a load, a transistor serving as a switch, and a diode. The load, the transistor, and the diode are connected in series between the terminals of an antenna. The transistor has an oxide semiconductor layer in which hydrogen concentration is 5×1019/cm3 or less. An off-state current of the transistor is 1×10?13 A or less. On/off of the transistor is controlled in accordance with a signal inputted to a gate of the transistor. The load is a resistor, a capacitor, or a combination of a resistor and a capacitor.

Abstract: Improved method of heat-treating a glass substrate, especially where the substrate is thermally treated (such as formation of films, growth of films, and oxidation) around or above its strain point. If devices generating heat are formed on the substrate, it dissipates the heat well. An aluminum nitride film is formed on at least one surface of the substrate. This aluminum nitride film acts as a heat sink and prevents local concentration of heat produced by the devices such as TFTs formed on the glass substrate surface.