Multimedia storage system with highly compact memory device
First Claim
1. A vertical memory cell formed in a trench in a substrate, said vertical memory cell comprising:
- a buried source region;
a drain region;
a channel region formed between said buried source region and said drain region;
a floating gate positioned in operative relation to said buried source region, said drain region and said channel region; and
a control gate insulated from said floating gate,wherein said floating gate includes a first segment positioned vertically in said trench and a second segment positioned horizontally, said first segment being spaced from said drain region by a first distance and said second segment being spaced from said drain region by a second distance less than said first distance.
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Abstract
A highly compact nonvolatile solid state memory core is provided that stores and reproduces both digital and analog signals for multimedia applications. The memory core includes vertical electrically erasable and programmable read only memories (EEPROM) cells having, for example, a stacked gate or a split channel configuration. An array of EEPROM cells on the same chip is prewritten and is used as a reference for digital-analog conversions and for memory cell programming. An intelligent write method allows each memory cell to either store an analog signal or multiple digital signals. Based on the previously stored signal, the intelligent write method determines whether to charge or to discharge the floating gate associated with the selected memory cell. Thus, full erasure is not required prior to programming each memory cell. The present invention significantly increases the density of memory cell arrays while prolonging the useful life of the array.
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Citations
39 Claims
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1. A vertical memory cell formed in a trench in a substrate, said vertical memory cell comprising:
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a buried source region; a drain region; a channel region formed between said buried source region and said drain region; a floating gate positioned in operative relation to said buried source region, said drain region and said channel region; and a control gate insulated from said floating gate, wherein said floating gate includes a first segment positioned vertically in said trench and a second segment positioned horizontally, said first segment being spaced from said drain region by a first distance and said second segment being spaced from said drain region by a second distance less than said first distance. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. The vertical memory cell formed in a substrate comprising:
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a buried source region; a drain region; a channel region formed between said buried source region and said drain region; a floating gate positioned in operative relation to said buried source region, said drain region, and said channel region; and a control gate insulated from said floating gate, wherein said drain region includes an extended drain region formed from polysilicon. - View Dependent Claims (9, 10, 11, 12)
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13. A vertical memory cell formed in a substrate comprising:
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a buried source region; a drain region; a channel region formed between said buried source region and said drain region; a floating gate positioned in operative relation to said buried source region, said drain region, and said channel region; a control gate insulated from said floating gate; and an erase/program gate positioned between said drain region and said control gate and in operative relation to said floating gate, wherein said cell is programmed by electrons tunneling from said erase/program gate to said floating gate and erased by electrons tunneling from said floating gate to said erase/program gate.
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14. A vertical memory cell formed in a substrate comprising:
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a buried source region; a drain region; a channel region formed between said buried source region and said drain region; a floating gate positioned in operative relation to said buried source region, said drain region, and said channel region; and a control gate insulated from said floating gate; and an erase/program gate positioned between said drain region and said control gate and in operative relation to said floating gate, wherein said erase/program gate is positioned above said drain region. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A vertical memory cell formed in a substrate comprising:
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a floating gate transistor formed in a first trench in said substrate; a series transistor formed in a second trench in said substrate, said second trench vertically aligned with said first trench; a buried source region; a drain region; a channel region formed between said buried source region and said drain region; a floating gate positioned in operative relation to said buried source region, said drain region, and said channel region; and a control gate insulated from said floating gate, wherein said first and second transistors share said channel region, and wherein said floating gate is formed in said first trench. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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Specification