Ultra high density flash memory having vertically stacked devices
First Claim
1. A memory cell, comprising:
- a pillar of semiconductor material extending outwardly from a working surface of a substrate to form source/drain and body regions, the pillar having a number of sides;
at least one pair of vertically stacked floating gates, each pair associated with a side of the pillar, a dielectric disposed between the floating gates within each pair; and
one or more control gates, each control gate associated with at least one floating gate so as to allow selective storage and retrieval of data on the floating gates.
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Abstract
An ultra high density flash EEPROM provides increased nonvolatile storage capacity. A memory array includes densely packed memory cells, each cell having a pillar of semiconductor material that extends outwardly from a working surface of a substrate. The pillar includes source/drain and body regions and has a number of sides. A pair of vertically stacked floating gates is included on at least one of two sides of the pillar. A control gate line also passes through each memory cell. Each memory cell is associated with a control gate line so as to allow selective storage and retrieval of data on the floating gates of the cell. Both bulk semiconductor and silicon-on-insulator embodiments are provided. If a floating gate transistor is used to store a single bit of data, an area of only F2 is needed per bit of data, where F is the minimum lithographic feature size. If multiple charge states (more than two) are used, an area of less than F2 is needed per bit of data.
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Citations
13 Claims
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1. A memory cell, comprising:
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a pillar of semiconductor material extending outwardly from a working surface of a substrate to form source/drain and body regions, the pillar having a number of sides; at least one pair of vertically stacked floating gates, each pair associated with a side of the pillar, a dielectric disposed between the floating gates within each pair; and one or more control gates, each control gate associated with at least one floating gate so as to allow selective storage and retrieval of data on the floating gates. - View Dependent Claims (2, 3, 4)
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5. A memory device, comprising:
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an array of memory cells, each cell including a number of transistors formed around a common pillar of semiconductor material that forms source/drain and body regions for the transistors and at least one pair of vertically stacked floating gates disposed adjacent to the sides of the pillar; a plurality of control gate lines that are substantially parallel in a first direction, each control gate line allowing selective storage and retrieval of data on ones of the floating gates; at least two source/drain interconnection lines, each source/drain interconnection line interconnecting ones of the source/drain regions of ones of the memory cells; and a plurality of data lines, each data line interconnecting ones of the source/drain regions of ones of the memory cells. - View Dependent Claims (6, 7)
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8. A memory cell that is fabricated upon a substrate, the memory cell comprising:
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a semiconductor pillar of a first conductivity type formed upon the substrate and having top and side surfaces; a first source/drain region, of a second conductivity type, formed proximal to an interface between the pillar and the substrate; a second source/drain region, of the second conductivity type, formed in a portion of the pillar that is distal to the substrate and separate from the first source/drain region; a third source/drain region, of the second conductivity type, formed in a portion of the pillar that is distal to the substrate and between the first and the second source/drain regions; a gate dielectric formed on at least a portion of the side surface of the pillar; at least one pair of vertically stacked floating gates, each pair substantially adjacent to a portion of the side surface of the pillar and separated therefrom by the gate dielectric; one or more control gate lines, each of which is substantially adjacent to at least one of the floating gates and insulated therefrom; and an intergate dielectric, interposed between each of the substantially adjacent floating and control gate lines. - View Dependent Claims (9, 10)
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11. A nonvolatile memory array that is fabricated upon a substrate, the memory array comprising:
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a plurality of memory cells, each memory cell including; a semiconductor pillar of a first conductivity type formed upon the substrate and having top and side surfaces; a first source/drain region, of a second conductivity type, formed proximal to an interface between the pillar and the substrate; a second source/drain region, of the second conductivity type, formed in a portion of the pillar that is distal to the substrate and separate from the first source/drain region; a third source/drain region, of the second conductivity type, formed in a portion of the pillar that is distal to the substrate and between the first and the second source/drain regions; a gate dielectric, formed on at least a portion of the side surface of the pillar; at least one pair of vertically stacked floating gates, each pair substantially adjacent to a portion of the side surface of the pillar and separated therefrom by the gate dielectric; at least one control gate line, substantially adjacent to at least one of the floating gates and insulated therefrom; and an intergate dielectric, interposed between each of the substantially adjacent floating gates and control gate lines; one or more first source/drain interconnection lines interconnecting ones of the first source/drain regions of ones of the memory cells; one or more second source/drain interconnection lines interconnecting ones of the second source/drain regions of ones of the memory cells; and a plurality of data lines, each data line interconnecting ones of the third source/drain regions of ones of the memory cells. - View Dependent Claims (12, 13)
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Specification