Process for forming an electrically programmable read-only memory cell
First Claim
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1. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
- forming a vertical edge adjacent to a primary surface of a semiconductor substrate;
forming a first doped region and a second doped region, wherein;
the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface;
the second doped region lies adjacent to the vertical edge and the primary surface, wherein a bottom of the second doped region at the vertical edge lies at a first elevation; and
a channel region adjacent to the vertical edge that lies between the first and second doped regions, wherein the channel region includes a first portion adjacent to the first doped region and a second portion adjacent to the second doped region;
forming a floating gate adjacent to the first portion of the channel region, wherein;
the floating gate has a highest point adjacent to the vertical edge; and
the highest point lies at a second elevation that is lower than and spaced apart from the first elevation; and
the step of forming the floating gate is performed after the step of forming the vertical edge;
forming a control gate adjacent to the first doped region; and
forming a select gate adjacent to the control gate and the second portion of the channel region.
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Abstract
A semiconductor device is formed having a floating gate memory cell (11) that has its channel region (33) oriented vertically with a portion of the channel region (33) that is not capacitively coupled to a floating gate (32). The memory cell (11) is less likely to be over-erased and may be programmed by source-side injection. The cell (11) may not need to be repaired after erasing. Less power may be consumed during programming compared to hot electron injection and Fowler-Nordheim tunneling.
290 Citations
23 Claims
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1. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
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forming a vertical edge adjacent to a primary surface of a semiconductor substrate; forming a first doped region and a second doped region, wherein; the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface; the second doped region lies adjacent to the vertical edge and the primary surface, wherein a bottom of the second doped region at the vertical edge lies at a first elevation; and a channel region adjacent to the vertical edge that lies between the first and second doped regions, wherein the channel region includes a first portion adjacent to the first doped region and a second portion adjacent to the second doped region; forming a floating gate adjacent to the first portion of the channel region, wherein; the floating gate has a highest point adjacent to the vertical edge; and the highest point lies at a second elevation that is lower than and spaced apart from the first elevation; and the step of forming the floating gate is performed after the step of forming the vertical edge; forming a control gate adjacent to the first doped region; and forming a select gate adjacent to the control gate and the second portion of the channel region. - View Dependent Claims (2, 3, 13, 14, 15, 16, 17, 18, 19, 20)
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4. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
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forming a vertical edge adjacent to a primary surface of a semiconductor substrate; forming a first doped region, a second doped region and a third doped region, wherein; the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface; the second doped region lies adjacent to the vertical edge and the primary surface, wherein a bottom of the second doped region at the vertical edge lies at a first elevation; a channel region adjacent to the vertical edge and lies between the first and second doped regions, wherein the channel region includes a first portion adjacent to the first doped region and a second portion adjacent to the second doped region; and the third doped region lies adjacent to the primary surface and is spaced apart from the second doped region; forming a floating gate adjacent to the first portion of the channel region, wherein; the floating gate has a highest point adjacent to the vertical edge; and the highest point lies at a second elevation that is lower than and spaced apart from the first elevation; and the step of forming the floating gate is performed after the step of forming the vertical edge; forming a control gate adjacent to the floating gate; and forming a select gate adjacent to the primary surface, the second doped region, and third doped region. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
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21. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
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forming a vertical edge adjacent to a primary surface of a semiconductor substrate; forming a first doped region, a second doped region and a third doped region, wherein; the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface; the second doped region lies adjacent to the vertical edge and the primary surface; a channel region adjacent to the vertical edge and lies between the first and second doped regions; and the third doped region lies adjacent to the primary surface and is spaced apart from the second doped region; forming a floating gate adjacent to a first portion of the channel region, wherein the first portion is less than all of the channel region; forming a field isolation region after the step of forming the floating gate; forming a control gate adjacent to the floating gate but not the channel region; and forming a select gate adjacent to the primary surface, the second doped region, and third doped region.
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22. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
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forming a vertical edge adjacent to a primary surface of a semiconductor substrate; forming a first doped region, a second doped region and a third doped region, wherein; the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface; the second doped region lies adjacent to the vertical edge and the primary surface; a channel region adjacent to the vertical edge and lies between the first and second doped regions; and the third doped region lies adjacent to the primary surface and is spaced apart from the second doped region; forming a floating gate adjacent to a first portion of the channel region, wherein the first portion is less than all of the channel region; forming a field isolation region along the vertical edge and adjacent to the floating gate; forming a control gate adjacent to the floating gate but not the channel region; and forming a select gate adjacent to the primary surface, the second doped region, and third doped region.
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23. A process for forming a semiconductor device including an electrically programmable read-only memory cell comprising the steps of:
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forming a vertical edge adjacent to a primary surface of a semiconductor substrate; forming a first doped region and a second doped region, wherein; the first doped region lies adjacent to the vertical edge and spaced apart from the primary surface; the second doped region lies adjacent to the vertical edge and the primary surface; and a channel region adjacent to the vertical edge and lies between the first and second doped regions; forming a floating gate adjacent to a first portion of the channel region; forming a field isolation region along the vertical edge and adjacent to the floating gate; forming a control gate adjacent to the first doped region; and forming a select gate adjacent to; the control gate; and a second portion of the channel region that is different from the first portion of the channel region.
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Specification