FLASH MEMORY CELL ON SeOI HAVING A SECOND CONTROL GATE BURIED UNDER THE INSULATING LAYER
First Claim
1. A flash memory cell comprising:
- an insulating layer on a base substrate;
a thin film layer of semiconductor material on the insulating layer to form a semiconductor-on-insulator substrate;
a channel in the thin film layer, wherein the channel forms part of a field effect transistor (FET);
a gate dielectric layer on the thin film layer above the channel;
a floating gate on the gate dielectric layer;
an inter-gate dielectric layer on the floating gate;
a front control gate on the inter-gate dielectric layer above the floating gate and separated therefrom by the inter-gate dielectric; and
a back control gate within the base substrate directly under and adjacent the insulating layer.
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Accused Products
Abstract
The invention relates to a flash memory cell having a FET transistor with a floating gate on a semiconductor-on-insulator (SOI) substrate composed of a thin film of semiconductor material separated from a base substrate by an insulating buried oxide (BOX) layer, The transistor has in the thin film, a channel, with two control gates, a front control gate located above the floating gate and separated from it by an inter-gate dielectric, and a back control gate located within the base substrate directly under the insulating (BOX) layer and separated from the channel by only the insulating (BOX) layer. The two control gates are designed to be used in combination to perform a cell programming operation. The invention also relates to a memory array made up of a plurality of memory cells according to the first aspect of the invention, which can be in an array of rows and columns, and a method of fabricating such memory cells and memory arrays.
103 Citations
18 Claims
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1. A flash memory cell comprising:
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an insulating layer on a base substrate; a thin film layer of semiconductor material on the insulating layer to form a semiconductor-on-insulator substrate; a channel in the thin film layer, wherein the channel forms part of a field effect transistor (FET); a gate dielectric layer on the thin film layer above the channel; a floating gate on the gate dielectric layer; an inter-gate dielectric layer on the floating gate; a front control gate on the inter-gate dielectric layer above the floating gate and separated therefrom by the inter-gate dielectric; and a back control gate within the base substrate directly under and adjacent the insulating layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of fabricating a flash memory cell comprising:
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forming an insulating layer on a base substrate; forming a thin film layer of semiconductor material on the insulating layer to form a semiconductor-on-insulator substrate; forming a channel in the thin film layer, wherein the channel forms part of a field effect transistor (FET); forming a gate dielectric layer on the thin film layer above the channel; forming a floating gate on the gate dielectric layer; forming an inter-gate dielectric layer on the floating gate to thereby electrically isolate the floating gate; forming a front control gate on the inter-gate dielectric layer above the floating gate and separated therefrom by the inter-gate dielectric; and forming a back control gate within the base substrate directly under and adjacent the insulating layer, wherein the front and back control gates are designed to be used in combination to perform a cell programming operation.
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18. A method of fabricating a memory array made of a plurality of FETs and DRAM cells, which comprises:
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forming an insulating layer on a base substrate; forming a thin film layer of semiconductor material on the insulating layer to form a semiconductor-on-insulator substrate; forming a plurality of channels in the thin film layer, wherein each of the plurality of channels forms part of a memory cell in an array; forming a trench in each of the plurality of channels created in the thin film layer; forming a gate dielectric layer on the walls of each of the plurality of trenches; forming a gate in each of the plurality of trenches on the gate dielectric layer by filling the trench with a gate material; forming the inter-gate dielectric layer on a first subset of the plurality of the floating gates; forming the front control gate on the inter-gate dielectric layer, for each of the cells of the first subset to thereby create a plurality of FET memory cells having floating gates; and forming the front control gate directly on the gate material filling a second subset of trenches, different from the first subset, to create a plurality of DRAM memory cells having floating channels.
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Specification