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Nonvolatile semiconductor memory having three dimension charge confinement
| Details |
Inventors: Dawson, L. Ralph; Osbourn, Gordon C.; Peercy, Paul S.; Weaver, Harry T.; Zipperian, Thomas E.;
Assignee: The United States of America as represented by the United States (Washington, DC)
Primary Examiner: James; Andrew J.
Assistant Examiner: Van Ngo; Ngan
Attorney, Agent or Firm: Ojanen; Karla, Chafin; James H., Moser; William R.
A layered semiconductor device with a nonvolatile three dimensional memory comprises a storage channel which stores charge carriers. Charge carriers flow laterally through the storage channel from a source to a drain. Isolation material, either a Schottky barrier or a heterojunction, located in a trench of an upper layer controllably retains the charge within the a storage portion determined by the confining means. The charge is retained for a time determined by the isolation materials' nonvolatile characteristics or until a change of voltage on the isolation material and the source and drain permit a read operation. Flow of charge through an underlying sense channel is affected by the presence of charge within the storage channel, thus the presences of charge in the memory can be easily detected. |
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DETAILED DESCRIPTION It is an object of this invention to provide a nonvolatile memory where charge is controllably confined in a quantum well formed by a double heterojunction.
It is another object of this invention to provide a field effect transistor (FET) acting as a nonvolatile memory element.
It is also an object of this invention to provide a nonvolatile memory FET, controlled through standard FET action, where charge flows only along, never perpendicular to, a channel in the gate region.
Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following description or may be learned by practice of the invention.
The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention may comprise a nonvolatile semiconductor device comprising a semiconductor substrate; a storage channel; a first barrier layer between the storage channel and the substrate surface; a second barrier layer covering the opposite surface of the storage channel; and isolation means for controllably permitting charge to flow into or out of the boundaries or perimeter of a storage portion of the storage channel, and for retaining charge in the storage portion.
In a preferred embodiment of the invention, the isolation means is a Schottky barrier formed by a metal ring in a groove in the second barrier around the perimeter of the storage portion.
Application of a voltage to the ring controls the flow of current through the isolation means into and out of the storage channel.
The device also may include a sense channel extending under the storage channel between the first barrier layer and the substrate, a gate electrode radially inside and vertically above the storage area, and external electrodes for passing current through the sense channel
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