Semiconductor memory device using vertical-channel transistors
First Claim
1. An SRAM device comprising:
- a plurality of word lines;
a plurality of bit lines; and
a plurality of static memory cells each including a first, second, third, fourth, fifth, and sixth transistors,wherein gates of said fifth and sixth transistors are coupled to said word lines,wherein source and drain regions of said fifth and sixth transistors are formed inside a semiconductor substrate,wherein channel regions, source and drain regions of said first and second transistors are formed by depositing three poly-silicon layers above a substrate surface of the semiconductor substrate,wherein vertical sides of said three poly-silicon layers, which surfaces are vertical against said substrate surface, are completely surrounded by a gate layer and having a dioxide layer inbetween,wherein some of said first, second, third, fourth, fifth, and sixth transistors are disposed on different surfaces from each other, andwherein said different surfaces are electrically connected through a vertical interconnect element.
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Abstract
The invention provides a semiconductor memory device comprising a plurality of word lines, a plurality of bit lines, and a plurality of static memory cells each having a first, second, third, fourth, fifth, and sixth transistors. While each of channels of the first, second, third, and fourth transistors are formed vertical against a substrate of the semiconductor memory device. Each of semiconductor regions forming a source or a drain of the fifth and sixth transistors forms a PN junction against the substrate. According to another aspect of the invention, the SRAM device of the invention has a plurality of SRAM cells, at least one of which is a vertical SRAM cell comprising at least four vertical transistors onto a substrate, and each vertical transistor includes a source, a drain, and a channel therebetween aligning in one aligning line which penetrates into the substrate surface at an angle greater than zero degree.
39 Citations
20 Claims
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1. An SRAM device comprising:
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a plurality of word lines; a plurality of bit lines; and a plurality of static memory cells each including a first, second, third, fourth, fifth, and sixth transistors, wherein gates of said fifth and sixth transistors are coupled to said word lines, wherein source and drain regions of said fifth and sixth transistors are formed inside a semiconductor substrate, wherein channel regions, source and drain regions of said first and second transistors are formed by depositing three poly-silicon layers above a substrate surface of the semiconductor substrate, wherein vertical sides of said three poly-silicon layers, which surfaces are vertical against said substrate surface, are completely surrounded by a gate layer and having a dioxide layer inbetween, wherein some of said first, second, third, fourth, fifth, and sixth transistors are disposed on different surfaces from each other, and wherein said different surfaces are electrically connected through a vertical interconnect element. - View Dependent Claims (2, 4, 5, 6, 7, 8, 9)
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3. A method for forming a SRAM device comprising a plurality of word lines, a plurality of bit lines, and a plurality of static memory cells each including a first, second, third, fourth, fifth, and sixth transistors, wherein gates of said fifth and sixth transistors are coupled to said word lines, wherein source and drain regions of said fifth and sixth transistors are formed inside a semiconductor substrate, comprising:
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depositing three poly-silicon layers above a substrate surface of the semiconductor substrate to form channel regions, source and drain regions of said first and second transistors; completely surrounding vertical sides of said three poly-silicon layers, which surfaces are vertical against said substrate surface, by a gate layer and providing a dioxide layer in-between; disposing some of said first, second, third, fourth, fifth, and sixth transistors on different surfaces from each other, said different surfaces being electrically connected through a vertical interconnect element, wherein said three poly-silicon layers includes a first, second, and third poly-silicon layers, and wherein said first and second transistors are formed by steps of; depositing the first poly-silicon layer which forms said drain regions, depositing the second poly-silicon layer above said first poly-silicon layer, which forms said channel regions, depositing the third poly-silicon layer above said second poly-silicon layer, which forms said source regions, etching said first, second, and third poly-silicon layers to form columns, forming said dioxide layer around said vertical sides, and depositing said gate layer around said dioxide layer. - View Dependent Claims (19)
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10. An SRAM device comprising:
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a plurality of word lines; a plurality of bit lines; and a plurality of static memory cells each including a first, second, third, fourth, fifth, and sixth transistors, wherein gates of said fifth and sixth transistors are coupled to said word lines, wherein channel regions, source and drain regions of said fifth and sixth transistors are formed inside a semiconductor substrate such that currents flow via said channel regions aligning in a first direction, wherein channel regions, source and drain regions of said first and second transistors are formed by depositing three poly-silicon layers above a substrate surface of the semiconductor substrate such that currents flow via said channel regions aligning in a second direction which crosses said first direction at an angle greater than zero degree and smaller than 90 degrees, wherein aligning sides of said three poly-silicon layers, which surfaces are parallel with said second direction, are completely surrounded by a gate layer having a dioxide layer inbetween, wherein some of said first, second, third, fourth, fifth, and sixth transistors are disposed on different surfaces each other, and wherein said different surfaces are electrically connected through a vertical interconnect element. - View Dependent Claims (11, 13, 14, 15, 16, 17, 18)
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12. A method for forming a SRAM device comprising a plurality of word lines, a plurality of bit lines, and a plurality of static memory cells each including a first, second, third, fourth, fifth, and sixth transistors, wherein gates of said fifth and sixth transistors are coupled to said word lines, wherein channel regions, source and drain regions of said fifth and sixth transistors are formed inside a semiconductor substrate such that currents flow via said channel regions aligning in a first direction, comprising:
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depositing three poly-silicon layers above a substrate surface of the semiconductor substrate to form channel regions, source and drain regions of said first and second transistors such that currents flow via said channel regions aligning in a second direction which crosses said first direction at an angle greater than zero degree and smaller than 90 degrees; completely surrounding aligning sides of said three poly-silicon layers, which surfaces are parallel with said second direction, by a gate layer and providing a dioxide layer in-between; depositing some of said first, second, third, fourth, fifth, and sixth transistors on different surfaces each other, said different surfaces being electrically connected through a vertical interconnect element, wherein said three poly-silicon layers includes a first, second, and third poly-silicon layers, and wherein said first and second transistors are formed by steps of; depositing the first poly-silicon layer which forms said drain regions, depositing the second poly-silicon layer above said first poly-silicon layer, which forms said channel regions, depositing the third poly-silicon layer above said second poly-silicon layer, which forms said source regions, etching said first, second, and third poly-silicon layers to form columns, forming said dioxide layer around said vertical sides, and depositing said gate layer around said dioxide layer. - View Dependent Claims (20)
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Specification