Semiconductor memory device

Details Semiconductor memory device Semiconductor memory device

1999-02-26

2001-01-23

Hoang, Huan (Department: 2818)

Static information storage and retrieval

Systems using particular element

Capacitors

C365S145000, C365S195000, C365S189090, C365S226000

Reexamination Certificate

active

06178108

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor memory device and mainly to the technology which may be effectively applied to a dynamic RAM (Random Access Memory) of large capacity utilizing a high dielectric or ferro-dielectric material for a memory capacitor.
In a dynamic RAM, the memory capacity is increased to
1
G bits from about 256M bits. In order to increase the memory capacity as explained above, the memory size must further be reduced.
Moreover, it is suggested in the Japanese Patent Application Laid-open Nos. SH062-84491 and HEI6-215563 that a circuit for supplying a voltage to the plate electrode of such a memory capacitor must be improved to improve the performance of a semiconductor memory device or to prevent malfunction thereof.
SUMMARY OF THE INVENTION
When a high dielectric material (for example, Ta2O5 film) or a ferro-dielectric material (for example, BST, PZT film) is used as the dielectric material for reduction in size of a memory capacitor, it has been proven through investigation by the inventors of the present invention that the following problems are generated. In the case of supplying an intermediate voltage to the plate (common) electrode of the memory capacitor, a comparatively longer time is required to keep the plate voltage of many capacitors connected in parallel at the intermediate voltage immediately after the power switch is turned on. However, in the dynamic RAM of the related art, no consideration is given to setting of the plate voltage, and when a control signal is input, the internal circuit starts its operation without relation to the rise of the plate voltage to enable a read or write operation.
However, according to the investigation by the inventors of the present invention, when an information memory capacitor is reduced in size, particularly by using a high dielectric material film or ferro-dielectric material film as explained above, the dielectric strength is rather low, giving an adverse effect to the characteristic itself, such as deterioration of the dielectric material film and the like.
It is therefore an object of the present invention to provide a semiconductor memory device which has a high integration density and high reliability with a simplified structure.
A summary of the typical features provided by the present invention will be explained briefly. That is, the semiconductor memory device comprises an address selection MOSFET and an information storing capacitor. In this semiconductor memory device having plurality of memory cells in which a plate voltage consisting of an intermediate potential is supplied to the common electrode of the information storing capacitors, a voltage detecting circuit or a timer circuit is used to directly detect that the plate voltage has reached a predetermined voltage near the intermediate voltage. When the plate voltage is less than the predetermined voltage, the word line selecting operation is inhibited or the pair bit lines are precharged to the intermediate voltage, and such operation is canceled after the plate voltage has reached the predetermined voltage to enable access to the memory device.
Other objects and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying drawings.


REFERENCES:
patent: 5754466 (1998-05-01), Arase

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