1. Field of the Invention
The present invention relates to a semiconductor device which stores data.
The present invention relates to a semiconductor device that includes a memory element and a circuit, which includes a thin film transistor (hereinafter referred to as a TFT), and a manufacturing method thereof.
It is to be noted that a semiconductor device in the present specification corresponds to a semiconductor device that can function as a general device by use of semiconductor characteristics, and electro-optical devices, semiconductor circuits, and electronic devices can all be considered semiconductor devices.
2. Description of the Related Art
Individual identification technology using semiconductor devices in which data is exchanged by wireless communication has been attracting attention in recent years. Individual identification technology using semiconductor devices has started to be utilized in production, management, or the like of individual objects and has started to be applied to authentication of individual people. This kind of semiconductor device is also called an RFID (Radio Frequency IDentification) tag, an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, and an electronic tag.
A semiconductor device typified by an RFID tag includes a memory element for storing information, and the data stored in the memory element can be exchanged between the RFID tag and an external reader device (also referred to as a reader) by wireless communication.
With respect to RFID devices equipped with these kinds of semiconductor memory elements, improvements in memory storage capacity have been desired in recent years. Because there are limitations on the extent to which memory storage capacity can be expanded using so-called electronically addressable active matrix elements in which one memory cell is installed per switching element, passive matrix elements with a simpler structure are needed. For these kinds of electronically addressable passive matrix elements, organic memory elements using conjugated polymers have been disclosed in Patent Document 1: Japanese Published Patent Application No. 2001-503183.