Casio Computer Co., Ltd.

Hiroyasu Yamada

Shinichi Shimomaki

Nobuyuki Yamamura

Naohiro Konya

Kyuya Baba

Hiroshi Matsumoto

Hiromitsu Ishii

Ikuhiro Yamaguchi

Tsuneharu Takeda

A memory element is formed of a thin film transistor. The thin film transistor has a semiconductor layer, a source electrode electrically connected to the semiconductor layer, a drain electrode electrically connected to the semiconductor layer and formed separately from the source electrode, a gate electrode for controlling formation of a channel of the semiconductor layer, and a gate insulation film for isolating the gate electrode and the semiconductor layer from each other and causing a hysteresis in the relation between the drain current and the gate circuit. The insulation film is a silicon nitride film whose composition ratio of silicon to nitrogen is in a range of approx. 0.85 to 1.1. According to this invention, the relation between the gate voltage and the drain current can be set to have a hysteresis. Therefore, the thin film transistor can be used as a memory element. Further, according to this invention, data can be written, erased and read out by selectively applying an electric field to the gate insulation film. Therefore, the thin film transistor can be used as a memory element.

Thin film transistor having memory function and method for using thin

Gd and Bi are used as sputter sources and are simultaneously sputtered, or sputtered alternately, each time in an amount for forming a layer having a thickness of 10 atoms or less, thereby forming a thin film on a substrate, in which Gd and Bi are mixed at a ratio of 4:3. The thin film is heat-treated to form a crystalline thin film having a phase represented by Gd.sub.4 Bi.sub.3.

Method of manufacturing crystalline thin-film of rare-earth compounds

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Hachioji, Japan

Kyuya Baba