The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 23, 1993
Filed:
Mar. 13, 1991
Hiroshi Matsumoto, Tachikawa, JP;
Hiroyasu Yamada, Fussa, JP;
Nobuyuki Yamamura, Hanno, JP;
Shinichi Shimomaki, Tokyo, JP;
Naohiro Konya, Hino, JP;
Kyuya Baba, Hachiooji, JP;
Casio Computer Co., Ltd., Tokyo, JP;
Abstract
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.