Multi-state NROM device
First Claim
Patent Images
1. A multi-state NROM transistor comprising:
- a substrate having a plurality of vertical pillars, each pillar comprising an upper doped region;
a gate insulator layer formed along facing sides of a first pillar and a second pillar of the plurality of vertical pillars;
a control gate formed overlying the gate insulator layers and the pillars; and
a lower doped region formed under a trench located between the first and second pillars, wherein during transistor operation the lower doped region couples a first channel that forms along the facing side of the first pillar and a second channel that forms along the facing side of the second pillar.
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Abstract
An array of NROM flash memory cells configured to store at least two bits per four F2. Split vertical channels are generated along each side of adjacent pillars. A single control gate is formed over the pillars and in the trench between the pillars. The split channels can be connected by an n+ region at the bottom of the trench or the channel wrapping around the trench bottom. Each gate insulator is capable of storing a charge that is adequately separated from the other charge storage area due to the increased channel length.
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Citations
35 Claims
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1. A multi-state NROM transistor comprising:
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a substrate having a plurality of vertical pillars, each pillar comprising an upper doped region;
a gate insulator layer formed along facing sides of a first pillar and a second pillar of the plurality of vertical pillars;
a control gate formed overlying the gate insulator layers and the pillars; and
a lower doped region formed under a trench located between the first and second pillars, wherein during transistor operation the lower doped region couples a first channel that forms along the facing side of the first pillar and a second channel that forms along the facing side of the second pillar. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An array of multi-state NROM transistors comprising:
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a substrate having a plurality of vertical pillars each separated by a trench, each pillar comprising an upper doped region, each upper doped region coupled to a first bitline of the array;
a plurality of gate insulator layers, each layer formed along facing sides of adjacent pillars of the plurality of vertical pillars;
a control gate formed in the trenches and overlying the plurality of vertical pillars, the control gate forming a wordline between a row of NROM transistors of the array of multi-state NROM transistors; and
a plurality of lower doped regions, each region formed under each trench, wherein during operation of the transistors each lower doped region couples a first channel that forms in a first pillar along a first side of a first trench and a second channel that forms in a second pillar along a second side of the first trench, each lower doped region coupled to a second bitline of the array. - View Dependent Claims (13, 14, 15, 16)
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17. An electronic system comprising:
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a processor circuit that generates memory control signals; and
an NROM flash memory device coupled to the processor circuit, the flash memory device having a plurality of multi-state NROM transistors, each transistor comprising;
a substrate having a plurality of vertical pillars, each pillar comprising an upper doped region and separated by a trench from adjacent pillars;
a first gate insulator layer formed along a first side of a first trench;
a second gate insulator layer formed along a second opposing side of the first trench;
a control gate formed in the first trench and overlying the plurality of vertical pillars; and
a lower doped region formed under the first trench, wherein during transistor operation the lower doped region couples a first channel that forms adjacent to the first gate insulator and a second channel that forms adjacent to the second gate insulator. - View Dependent Claims (18, 19, 20)
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21. A multi-state NROM transistor comprising:
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a substrate having a plurality of vertical pillars, each pillar comprising a doped region;
a gate insulator layer formed along facing sides of a first pillar and a second pillar of the plurality of vertical pillars; and
a control gate formed overlying the gate insulator layers and the pillars wherein during transistor operation a channel forms between a doped region of the first pillar and the doped region of the second pillar. - View Dependent Claims (22, 23)
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24. An array of multi-state NROM transistors comprising:
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a substrate having a plurality of vertical pillars with a trench between each pillar, each pillar comprising a doped region;
a plurality of gate insulator layers, each layer formed along opposing sides of each trench; and
a control gate formed in each trench and overlying the plurality of vertical pillars to form a wordline wherein during transistor operation a channel forms between a doped region of the first pillar and the doped region of the second pillar. - View Dependent Claims (25)
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26. A method for manufacturing a split-channel transistor, the method comprising:
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incising a substrate to form a plurality of trenches, each pair of trenches defining a pillar;
doping a region in an upper portion of each pillar;
doping a lower region under each trench;
forming a nitride storage region on each facing side of adjacent pillars; and
forming a control gate overlying the pillars and in the plurality of trenches wherein during a programming operation of the transistor, a channel is formed along the facing sides of adjacent pillars and are connected by the lower doped region, the lower doped region not being coupled to an electrical contact. - View Dependent Claims (27, 28, 29, 30, 31)
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32. A method for programming a split-channel having a pair of pillars forming a trench, each pillar having a source/drain region and the trench having a floating n+ diffusion region that has no electrical contact, nitride charge storage regions formed along facing sides of the trench and a control gate overlying the nitride charge storage regions and the pair of pillars, the method comprising:
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grounding a first source/drain region;
applying a gate voltage to the control gate; and
applying a drain voltage to a second source/drain region such that a channel forms along the facing sides of the trench between the first and second source/drain regions and under the trench. - View Dependent Claims (33)
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34. A method for programming a split-channel having a pair of pillars forming a trench, each pillar having a source/drain region, nitride charge storage regions formed along facing sides of the trench and a control gate overlying the nitride charge storage regions and the pair of pillars, the method comprising:
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grounding a first source/drain region;
applying a gate voltage to the control gate; and
applying a drain voltage to a second source/drain region such that a channel forms along the facing sides of the trench between the first and second source/drain regions and under the trench.
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35. A method for manufacturing a split-channel transistor, the method comprising:
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incising a substrate to form a plurality of trenches, each pair of trenches defining a pillar;
doping a region in an upper portion of each pillar;
forming a nitride storage region on each facing side of adjacent pillars; and
forming a control gate overlying the pillars and in the plurality of trenches wherein during a programming operation of the transistor, a channel is formed along the facing sides of adjacent pillars and are connected together under each trench.
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Specification