# US 5,350,933 A · Semiconductor CMOS static RAM with overlapping thin film transistors

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- Number: US 5,350,933 A
- Document ID: US5350933A
- Status: Granted
- Kind: A
- Application number: 07/656,596
- Filed: 1991-02-19
- Granted: 1994-09-27
- Earliest claimed: 1990-02-21
- Assignees: Sony Corporation
- Inventors: Ikuo Yoshihara
- Web page: https://patentgrep.com/patent/US5350933A

## CPC

- H10B 10/125: {the MOSFET being a thin film transistor [TFT]}
- Y10S 257/903: FET configuration adapted for use as static memory cell
- H10B: ELECTRONIC MEMORY DEVICES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A pair of load transistors of a flip-flop circuit constituting a memory cell consist of thin film transistors, and channel regions of the pair of load transistors overlap drain regions of the transistors through a gate insulating film. For this reason, a channel length of the load transistor can be sufficiently increased, and a leakage current of the load transistor can be reduced.

## Claims

### Claim 1

A semiconductor memory comprising a memory cell having a flip-flop circuit consisting of a pair of driver transistors of a first conductivity type channel and a pair of load transistors of a second conductivity type channel, and a pair of access transistors,
wherein said pair of load transistors of the second conductivity type channel are formed by semiconductor thin films wherein each of the pair of load transistors have a channel region and a drain region such that the drain region of one of said pair of load transistors of the second conductivity type channel overlaps the channel region of the other of the pair of load transistors through a gate insulating film and the drain region of the other of the pair of load transistors overlap the channel region of the one of the pair of load transistors through the gate insulating film.

### Claim 2 (depends on 1)

A semiconductor memory according to claim 1, wherein source regions of said pair of load transistors of the second conductivity type channel extend in opposite directions and are connected to power source lines between which the memory cell is located.

### Claim 3

A semiconductor memory comprising a memory cell having a flip-flop circuit consisting of a pair of driver transistors of a first conductivity type channel and a pair of load transistors of a second conductivity type channel, and a pair of access transistors,
wherein said pair of load transistors of the second conductivity type channel are formed by semiconductor thin films each having a channel region and a drain region such that the drain region of one of said pair of load transistors of the second conductivity type channel overlaps the channel region of the other of the pair of load transistors through a gate insulating film and the drain region of the other of the pair of load transistors overlap the channel region of the one of the pair of load transistors through the gate insulating film; and further wherein widths of said semiconductor thin films of said pair of load transistors of the second conductivity type channel are larger at a portion of said drain region than at a portion of said channel region.

### Claim 4

A semiconductor memory comprising a memory cell having a flip-flop circuit consisting of a pair of driver transistors of a first conductivity type channel and a pair of load transistors of a second conductivity type channel, and a pair of access transistors,
wherein said pair of load transistors of the second conductivity type channel are formed by semiconductor thin films wherein each of the pair of load transistors have a channel region and a drain region such that the drain regions of one of said pair of load transistors of the second conductivity type channel overlaps the channel region of the other of the pair of load transistors through a gate insulating film and the drain region of the other of the pair of load transistors overlap the channel region of the one of the pair of load transistors through the gate insulating film, wherein said pair of driver transistors of the first conductivity type channel are formed by semiconductor thin films such that channel regions and drain regions of said pair of driver transistors of the first conductivity type channel overlap through the gate insulating film.