In recent years, a semiconductor device having various functions, in which a plurality of circuits are integrated over an insulated surface, has been developed. Moreover, a semiconductor device which can conduct wireless transmission/reception of data by providing an antenna has been developed. Such a semiconductor device is referred to as a wireless chip (also referred to as an ID tag, an IC tag, an IC chip, a RF (Radio Frequency) tag, a wireless tag, an electronic tag, or a RFID (radio frequency identification)) tag, and has already brought to part of the market.
Many of these semiconductor devices that have already been put into practical use have a circuit (also referred to as an IC (integrated circuit) chip) using a semiconductor substrate such as an Si substrate and an antenna, and the IC chip includes a memory circuit (also referred to as a memory), a control circuit, and the like. In particular, by providing a memory circuit which can store much data, a semiconductor device with high added value providing higher performance can be provided. In addition, such semiconductor devices are required to be manufactured at low cost. In recent years, an organic memory and the like using an organic compound for a memory circuit and the like, have been actively developed (for example, Reference 1: Japanese Patent Application Laid-Open No. 2002-26277).
As a memory circuit, a DRAM (dynamic random access memory), an SRAM (static random access memory), an FeRAM (ferroelectric random access memory), a mask ROM (read only memory), an EPROM (electrically programmable read only memory), an EEPROM (electrically erasable and programmable read only memory), a flash memory, and the like are given. Among them, a DRAM and a SRAM are volatile memory circuits in which data is erased when power source is turned off; therefore, it is necessary to write data every time the power source is turned on. Although an FeRAM is a nonvolatile memory circuit, a manufacturing step thereof is increased because a capacitor element including a ferroelectric layer is used. A mask ROM has a simple structure; however, it is necessary to write data during a manufacturing process, and data cannot be rewritten. An EPROM, an EEPROM, and a flash memory are nonvolatile memory circuits; however, the number of manufacturing steps thereof is increased because an element having two gate electrodes is used.
To form a memory element by using an organic compound, the organic compound is provided between a pair of electrodes. When a thickness of the organic compound layer is increased, current does not easily flow and writing voltage is increased. Meanwhile, when a thickness of an organic compound layer is reduced to reduce writing voltage, short-circuiting may be caused between the electrodes in an initial state. This may result in reduction of reliability of a memory device and a semiconductor device.