Patent EP0366146A2 successfully refreshed from Google Patents.
EP0366146A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Thin film transistor having memory function and method for using thin film transistor as memory element
Assignee: Casio Computer Co Ltd
•
Filing: 1989-10-27
•
Granted: —
•
Expires: 2009-10-27
Abstract
Abstract A memory element is formed of a thin film transistor. The thin film transistor has a semiconductor layer (4), a source electrode (6) electrically connected to the semiconductor layer, a drain electrode (7) electrically connected to the semiconductor layer and formed separately from the source electrode, a gate electrode (2) for controlling formation of a channel of the semiconductor layer, and a gate insulation film (3) for isolating the gate electrode (2) and the semiconductor layer (4) 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.
Inventors
- 👤 Hiroshi P.D. Dev.Div. Hamura R&D Center Matsumoto
- 👤 Hiroyasu P.D. Dev.Div. Hamura R&D Center Yamada
- 👤 Nobuyuki P.D. Dev.Div. Hamura R&D Center Yamamura
- 👤 Shinichi P.D. Dev.Div Hamura R&D Center Shimomaki
- 👤 Naohiro P.D. Dev.Div. Hamura R&D Center Konya
- 👤 Kyuya P.D. Dev.Div. Hamura R&D Center Baba
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 03:40
CPC Classifications
H; H10; H10B; H10B69/00; H10D; H10D30/00; H10D30/60; H10D30/69; H10D84/00; H10D84/60; H10D84/645
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
103 words
A memory element utilizing a hysteresis in the relation between a drain current and a gate voltage of a thin film transistor comprising: a thin film transistor having a semiconductor layer (4); a source electrode (6) electrically connected to said semiconductor layer; a drain electrode (7) electrically connected to said semiconductor layer and formed separately from said source electrode; a gate electrode (2) for controlling formation of a channel in said semiconductor layer; and insulation film means (3) for isolating said gate electrode (2) from said semiconductor layer (4) and causing a hysteresis in the relation between the drain current and gate voltage.
Claim 2
Dependent Claim
103 words
A memory element utilizing a hysteresis in the relation between a drain current and a gate voltage of a thin film transistor comprising: a thin film transistor having a semiconductor layer (4); a source electrode (6) electrically connected to said semiconductor layer; a drain electrode (7) electrically connected to said semiconductor layer and formed separately from said source electrode; a gate electrode (2) for controlling formation of a channel in said semiconductor layer; and insulation film means (3) for isolating said gate electrode (2) from said semiconductor layer (4) and causing a hysteresis in the relation between the drain current and gate voltage.
Claim 3
Dependent Claim
19 words
A memory element according to claim 1, characterized in that said insulation film means includes means for trapping charges.
Claim 4
Dependent Claim
21 words
A memory element according to claim 1, characterized in that said insulation film means includes a composition of silicon and nitrogen.
Claim 5
Dependent Claim
47 words
A memory element according to claim 1, characterized in that said insulation film means includes a silicon nitride film whose composition ratio Si/N of silicon to nitride lies within a range of 0.85 to 1.1 and whose thickness lies in a range of 1000 to 3000 angstrom.
Claim 6
Dependent Claim
41 words
A memory element according to claim 1, characterized in that said insulation film means includes a silicon nitride film (13b) having a function of trapping charges and a film (13a) of a composition different from that of said silicon nitride film.
Claim 7
Dependent Claim
50 words
A memory element according to claim 1, characterized in that said insulation film means includes a silicon nitride film (13b) whose composition ratio Si/N lies in a range of 0.85 to 1.1 and a silicon nitride film (13a) whose composition ratio Si/N lies in a range of 0.7 to 0.8.
Claim 8
Dependent Claim
28 words
A memory element according to claim 1, characterized in that said insulation film means includes a silicon nitride film (23b) and a film (23a) formed of ferroelectric material.
Claim 9
Dependent Claim
34 words
A memory element according to claim 1, characterized in that said insulation film means is constituted by a laminated structure of at least one insulation layer (3) and at least one semiconductor layer (18).
Claim 10
Dependent Claim
41 words
A memory element according to claim 1, characterized in that said insulation film means includes a silicon nitride film (22A) whose composition ratio Si/N varies in the thickness direction thereof and which has an area having a composition ratio of 1.0.
Claim 11
Dependent Claim
39 words
A memory element according to claim 1, characterized by further comprising means for writing data into said memory element, means for erasing data stored in said memory element and means for reading out data stored in said memory element.
Claim 12
Dependent Claim
31 words
A memory element according to claim 1, characterized in that said memory element further includes a glass substrate (1), and said thin film transistor is formed on the glass substrate (1).
Claim 13
Dependent Claim
81 words
A memory element for storing data, comprising: a thin film transistor comprising semiconductor layer means (4) for including semiconductor material and generating a channel therein; source means (6) connected to said semiconductor layer means, for supplying carriers to said channel; drain means (7) connected to said semiconductor layer means, for draining carriers from said channel; gate electrode means (2) for controlling formation of said channel; and insulation film means (3) for insulating said gate electrode means from said semiconductor layer means.
Claim 14
Dependent Claim
81 words
A memory element for storing data, comprising: a thin film transistor comprising semiconductor layer means (4) for including semiconductor material and generating a channel therein; source means (6) connected to said semiconductor layer means, for supplying carriers to said channel; drain means (7) connected to said semiconductor layer means, for draining carriers from said channel; gate electrode means (2) for controlling formation of said channel; and insulation film means (3) for insulating said gate electrode means from said semiconductor layer means.
Claim 15
Dependent Claim
34 words
A memory element according to claim 12, characterized in that said insulation film means includes means for causing a hysteresis in the relation between a current flowing in said channel and a gate voltage.
Claim 16
Dependent Claim
47 words
A memory element according to claim 13, characterized in that said insulation film means includes a silicon nitride film whose composition ratio Si/N of silicon to nitride lies within a range of 0.85 to 1.1 and whose thickness lies in a range of 1000 to 3000 angstrom.
Claim 17
Dependent Claim
62 words
A memory element according to claim 13, characterized in that said insulation film means includes a silicon nitride film (13b) whose composition ratio Si/N lies in a range of 0.85 to 1.1; and at least one of a silicon nitride film (13a) whose composition ratio Si/N lies in a range of 0.7 to 0.8, ferroelectric film (23a) and a semiconductor layer (18).
Claim 18
Dependent Claim
41 words
A memory element according to claim 13, characterized in that said insulation film means includes a silicon nitride film (22A) whose composition ratio Si/N varies in the thickness direction thereof and which has an area having a composition ratio of 1.0.
Claim 19
Dependent Claim
39 words
A memory element according to claim 12, characterized by further comprising means for writing data into said memory element, means for erasing data stored in said memory element and means for reading out data stored in said memory element.
Claim 20
Dependent Claim
105 words
A memory element using hysteresis between a drain current and gate voltage, comprising: thin film transistors (TM) arranged in a matrix form; each of the thin film transistors (TM) having: a semiconductor layer (4), source electrode (6) electrically connected to the semiconductor layer (4), a drain electrode (7) electrically connected to said semiconductor layer (4) and formed separately from said source electrode (6); a gate electrode (2) for controlling formation of a channel in said semiconductor layer (4), and insulation film means (3) for isolating said gate electrode (2) from said semiconductor layer (4) and causing a hysteresis between the drain current and gate voltage.
Claim 21
Dependent Claim
105 words
A memory element using hysteresis between a drain current and gate voltage, comprising: thin film transistors (TM) arranged in a matrix form; each of the thin film transistors (TM) having: a semiconductor layer (4), source electrode (6) electrically connected to the semiconductor layer (4), a drain electrode (7) electrically connected to said semiconductor layer (4) and formed separately from said source electrode (6); a gate electrode (2) for controlling formation of a channel in said semiconductor layer (4), and insulation film means (3) for isolating said gate electrode (2) from said semiconductor layer (4) and causing a hysteresis between the drain current and gate voltage.
Claim 22
Dependent Claim
60 words
A memory element according to claim 18, characterized by further comprising means (TS, RD, CD) for selecting at least one of the thin film transistors (TM), and means (TS, RD, CD, RG) for writing data into a selected thin film transistor, erasing data stored in a selected thin film transistor, and reading data stored in a selected thin film transistor.
Claim 23
Dependent Claim
30 words
A memory element according to claim 18, characterized by further comprising a glass substrate (1), and characterized in that said thin film transistors are formed on the glass substrate (1).
Claim 24
Independent Claim
118 words
A method for using a thin film transistor as a memory element, comprising the steps of: preparing a thin film transistor having a semiconductor layer (4), a source (6), a drain (7), a gate (2) and a gate insulation film; writing first data into said thin film transistor by applying a first voltage to said gate insulation film; writing second data different from the first data by applying a second voltage different from that of the first voltage to said gate insulation film; and reading data stored in said thin film transistor according to a current which flows in said channel and whose level is changed by a difference in the voltages pplied to said gate insulation film.
Claim 25
Independent Claim
118 words
A method for using a thin film transistor as a memory element, comprising the steps of: preparing a thin film transistor having a semiconductor layer (4), a source (6), a drain (7), a gate (2) and a gate insulation film; writing first data into said thin film transistor by applying a first voltage to said gate insulation film; writing second data different from the first data by applying a second voltage different from that of the first voltage to said gate insulation film; and reading data stored in said thin film transistor according to a current which flows in said channel and whose level is changed by a difference in the voltages pplied to said gate insulation film.
Claim 26
Dependent Claim
18 words
A method according to claim 21, characterized in that said first and second voltages are of opposite polarities.
Claim 27
Dependent Claim
60 words
A method according to claim 21, which further includes the steps of arranging said thin film transistors in a matrix form and selecting a desired one of said thin film transistors; and characterized in that said steps of writing the first data and writing and reading out the second data are effected with respect to said selected thin film transistor.
Claim 28
Dependent Claim
50 words
A method according to claim 21, characterized in that said step of preparing said thin film transistor includes a step of forming said insulation film which isolates said gate and semiconductor layer from each other and causes a hysteresis in the relation between the channel current and the gate voltage.
Claim 29
Dependent Claim
43 words
A method according to claim 24, characterized in that said step of forming said insulation film includes a step of forming said gate insulation film which includes a silicon nitride film whose composition ratio Si/N of silicon to nitride is larger than 0.85.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.