Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-08-20
2004-04-20
Nguyen, Cuong (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
Reexamination Certificate
active
06724038
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a memory element for a semiconductor memory device, in particular, a multibit memory cell, or the like.
There exist memory elements for semiconductor memory devices, in which a change is made from the basic structure, the memory elements having a storage capacitor and a selection transistor that is physically isolated from the capacitor for information storage.
In such memory elements for semiconductor memory devices, a number of line devices are provided that are substantially electrically insulated from one another in pairs, are formed in a semiconductor substrate of a first conductance type or in a surface area thereof, and are at least partially formed and disposed physically separated from one another in pairs by an intermediate area of the semiconductor substrate. Furthermore, an isolation area is provided there, which is composed of an substantially electrically insulating material that makes mechanical and electrical contact with the intermediate area, and in each case with an overlap area of each line device. In such a case, by applying to the line devices, in particular, to their overlap areas, and to the isolation area an electrical potential distribution in the isolation area in accordance with an information unit that is to be stored, it is possible, at least temporarily, to form at least one area with changed electrical and/or magnetic characteristics.
Conventional memory elements of this type are subject to the problem that the isolation area allows only an substantially physically cohesive change to the electrical and/or magnetic characteristics in the isolation area so that it is impossible to satisfactorily ensure strict physical isolation between the stored information contents, or information contents to be stored, and, hence, cross-talk between information contents that need to be distinguished, for example, a number of bits.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a memory element for a semiconductor memory device that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that ensures adequate discrimination between stored information contents in the memory element in a simple manner.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a memory element for a semiconductor memory device, including a semiconductor substrate of a first conductance type having a surface area, an intermediate area, and a number of line devices formed one of in the semiconductor substrate and in the surface area, the line devices substantially electrically insulated from one another in pairs and at least partially formed and disposed physically separated from one another in pairs by the intermediate area, an isolation area of an substantially electrically insulating material, the isolation area mechanically and electrically contacted with the intermediate area, and each of the line devices at a respective overlap area of each of the line devices, the isolation area having a number of material areas isolated from one another to form at least one area with at least one of changed electrical characteristics and changed magnetic characteristics in the isolation area, at least one of each of the material areas having free charge carriers and each of the material areas being able to have free charge carriers formed therein, and the line devices and the isolation area at least temporarily forming the at least one area when an electrical potential distribution is applied to the line devices and to the isolation area in the isolation area in accordance with an information unit that is to be stored. In the memory element, the overlap areas and the isolation area can at least temporarily form the at least one area when an electrical potential distribution is applied to the overlap areas and to the isolation area in the isolation area in accordance with an information unit that is to be stored. The memory element can be for a multibit memory cell.
The memory element according to the invention for a semiconductor memory device, in particular, a multibit memory cell or the like, is distinguished in that a number of material areas that are isolated from one another are provided to form the at least one area with changed or changeable electrical and/or magnetic characteristics in the isolation area, and in that the material areas have substantially free charge carriers, and/or free charge carriers can be formed in the material areas.
One basic idea of the present invention is, thus, to simplify and to assist the formation of changed electrical and/or magnetic characteristics in the isolation area by providing a number of material areas in the isolation area, which have free charge carriers and/or in which free charge carriers can be formed. This means that the electrical characteristics or magnetic characteristics can be formed comparatively easily, that is to say, with relatively small electrical potentials in the physically isolated material areas. In the process, local application results in the respectively provided information content also remaining in a local manner in the isolation area. Furthermore, further localization and, hence, avoidance of cross-talk are provided by the isolation of the number of material areas with respect to or from one another, with this isolation being provided, if appropriate, simply by physical separation.
For such a purpose, in accordance with another feature of the invention, the invention advantageously provides for the material areas to be embedded in the isolation area.
In accordance with a further feature of the invention, particularly highly localized structures are obtained if nanodots, or the like, are provided as the material areas. The expression nanodots means very small islands of a material B in a matrix composed of a material A. Alternatively, it is also feasible for a localized area B to be formed within the material A, with this area B having significantly changed electrical characteristics, for example, as a result of severe damage to the material A.
The major characteristic of the material areas in the isolation area is the presence of substantially free charge carriers or the capability to be able to form substantially free charge carriers in the material of the material areas in the isolation area. It is, thus, particularly advantageous for the material areas in the isolation area to have a metal, a semiconductor material, in particular, silicon, germanium and/or the like, possibly in an appropriately doped form, or to be formed from such a material.
In accordance with an added feature of the invention, it is advantageous, but not essential, for the material areas in the isolation area each to be formed substantially identically. This relates both to the geometric characteristics and to the electrical and/or magnetic characteristics of the material areas, and of the material on which these material areas are based.
The material areas in the isolation area may be formed in widely differing ways. For example, it is possible for the material areas of the isolation area to be formed or deposited as material areas that are deposited, but not all the way through, on a first insulator layer of the isolation area, and that are, then, embedded in a second insulator layer of the isolation area. On the other hand, the material areas of the isolation area may also be in the form of implantation regions in the isolation area.
If required, it is possible to carry out heat-treatment at comparatively high temperatures after forming the actual material areas in the isolation area. Accordingly, the corresponding material areas can be further reduced in size by an appropriate oxidation process, in order, in this way, to improve the information localization and the cross-talk behavior further.
In principle, it is feasible for the material areas and, in particular, the nanodots to be formed over the entire isolation area. However, it is particu
Greenberg Laurence A.
Locher Ralph E.
Nguyen Cuong
Stemer Werner H.
LandOfFree
Memory element for a semiconductor memory device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Memory element for a semiconductor memory device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Memory element for a semiconductor memory device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3227428