Nonvolatile semiconductor memory and method for driving the same
View Patent ↗To provide a NOR-type nonvolatile semiconductor memory that can inject electric charge into a charge accumulation layer through the use of an FN tunnel current without compromising an increase in the packing density of memory cells. The above problem is solved by a nonvolatile semiconductor memory in which nonvolatile semiconductor memory cells are arranged in a matrix, each nonvolatile semiconductor memory cell having an island semiconductor layer in which a drain diffusion layer formed in the upper part of the island semiconductor layer, a source diffusion layer formed in the lower part of the island semiconductor layer, a charge accumulation layer formed on a channel region of the side wall sandwiched between the drain diffusion layer and the source diffusion layer via a gate insulation film, and a control gate formed on the charge accumulation layer are formed. Further, bit lines connected to the drain diffusion layer are laid out in a column direction, control gate lines are laid out in a row direction, and source lines connected to the source diffusion layer are laid out in the column direction.
1. A nonvolatile semiconductor memory including a plurality of memory cells each comprising:
a source region, a channel region, and a drain region thereon in this order extending from a surface of the substrate in a direction perpendicular to the surface of the substrate and further including a charge accumulation layer, via a gate insulation film, on an outside surface of the channel region and a control gate formed, via an insulation layer, on an outside surface of the charge accumulation layer so as to cover the charge accumulation layer, the memory cells arranged on the substrate in a matrix with n rows and m columns and further comprising:
a plurality of source lines laid out in a column direction and connecting the source regions of the memory cells with each other;
a plurality of parallel bit lines laid out in the column direction in a layer different from the source lines and connecting the drain regions of the memory cells with each other;
a plurality of gate lines laid out in a row direction that is substantially perpendicular to the column direction and connecting the control gates of the memory cells with each other;
a plurality of transistors comprising a switch for electrically connecting a common source line to the plurality of source lines and for electrically disconnecting the common source line from the plurality of source lines, wherein one row of transistors is formed at intervals of p (p<n) rows of the matrix, the transistors each having a source region, a channel region, and a drain region formed in this order from a surface of the substrate in a direction perpendicular to the surface of the substrate, each source region being connected to the source line of a column to which the source region belongs;
read lines laid out in the row direction and connecting gates of the transistors with each other, the transistors aligned in a same row; and
wherein the common source lines connect the drain regions of the transistors with each other, the transistors being aligned in the same row.
2. The nonvolatile semiconductor memory according to claim 1 , wherein the source region, the channel region, and the drain region of the each transistor are formed concurrently with the source region, the channel region, and the drain region, respectively, of the each memory cell.
3. A method for writing into the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying 0 V or a positive first voltage to a selected bit line and a selected source line;
applying the positive first voltage to a non-selected bit line and a non-selected source line;
applying a positive second voltage to a selected gate line;
applying 0 V to a non-selected gate line;
applying 0 V to the read lines; and
applying a positive third voltage which is half the positive first voltage to the common source lines, electric charge is injected into the charge accumulation layer of a selected memory cell through a use of an FN tunnel current.
4. A method for reading the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying a positive first voltage to a selected gate line;
applying 0 V to a non-selected gate line;
applying 0 V to the source lines;
applying a positive second voltage to a selected bit line;
applying 0 V to a non-selected bit line and a common source line; and
applying a positive third voltage to the read lines, data is read from a selected memory cell.
5. A method for erasing the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying a positive first voltage to all the bit lines and all the source lines, applying 0 V to all gate lines; and
applying the positive first voltage to all the common source lines and the read lines, data of all the memory cells is erased at a time.
6. A method for erasing the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying a positive first voltage to all the bit lines and the source lines;
applying 0 V to a selected gate line;
applying a positive second voltage to a non-selected gate line; and
applying the positive first voltage to all the common source lines and the read lines, data of the memory cells connected to the selected gate line is erased at a time.
7. A method for erasing the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying a positive first voltage to a selected bit line and a selected source line;
applying a positive second voltage to a non-selected bit line and a non-selected source line;
applying 0 V to all gate lines;
applying the positive second voltage to all the read lines; and
applying a positive third voltage which is half a sum of the positive first voltage and the positive second voltage to all the common source lines, data of the memory cells connected to the selected bit line is erased at a time.
8. A method for erasing the nonvolatile semiconductor memory according to claim 1 , the method comprising:
applying a positive first voltage to a selected bit line and a selected source line;
applying a positive second voltage to a non-selected bit line and a non-selected source line;
applying 0 V to a selected gate line;
applying the positive second voltage to a non-selected control gate line;
applying the positive second voltage to the read lines; and
applying a positive third voltage which is half a sum of the positive first voltage and the positive second voltage to the common source lines, data of a selected memory cell is erased.
9. A nonvolatile semiconductor memory including a plurality of memory cells each comprising:
a source region, a channel region, and a drain region thereon in this order extending from a surface of the substrate in a direction perpendicular to the surface of a substrate and further including a charge accumulation layer via a gate insulation film, on an outside surface of the channel region and a control gate formed, via an insulation layer, on an outside surface of the charge accumulation layer so as to cover the charge accumulation layer, the memory cells arranged on the substrate in a matrix with n rows and m columns, and further comprising:
a plurality of source lines laid out in a column direction and connecting the source regions of the memory cells with each other;
a plurality of parallel bit lines laid out in the column direction in a layer different from the source lines and connecting the drain regions of the memory cells with each other;
a plurality of gate lines laid out in a row direction that is substantially perpendicular to the column direction and connecting the control gates of the memory cells with each other;
a plurality of transistors comprising a switch for electrically connecting a common source line to the plurality of source lines and for electrically disconnecting the common source line from the plurality of source lines, wherein one row of transistors is formed at intervals of p (p<n) rows of the matrix, the transistors each having a source region, a channel region, and a drain region formed in this order from a surface of the substrate in a direction perpendicular to the surface of the substrate, each source region being connected to the source line of a column to which the source region belongs;
read lines laid out in the row direction and connecting gates of the transistors with each other, the transistors aligned in a same row; and
wherein the common source lines connect the drain regions of the transistors with each other, the transistors being aligned in the same row, wherein the source region, the channel region, and the drain region of the each transistor are formed concurrently with the source region, the channel region, and the drain region, respectively, of the each memory cell.
10. A method for writing into the nonvolatile semiconductor memory according to claim 9 , the method comprising:
applying 0 V or a positive first voltage to a selected bit line and a selected source line, applying the positive first voltage to a non-selected bit line and a non-selected source line;
applying a positive second voltage to a selected gate line, applying 0 V to a non-selected gate line, applying 0 V to the read lines; and
applying a positive third voltage which is half the positive first voltage to the common source lines, electric charge is injected into the charge accumulation layer of a selected memory cell through a use of an FN tunnel current.
11. A method for reading the nonvolatile semiconductor memory according to claim 9 , the method comprising:
applying a positive first voltage to a selected gate line;
applying 0 V to a non-selected gate line;
applying 0 V to the source lines, applying a positive second voltage to a selected bit line, applying 0 V to a non-selected bit line and a common source line; and
applying a positive third voltage to the read lines, data is read from a selected memory cell.
12. A method for erasing the nonvolatile semiconductor memory according to claim 9 , the method comprising:
applying a positive first voltage to all the bit lines and all the source lines;
applying 0 V to all gate lines; and
applying the positive first voltage to all the common source lines and the read lines, data of all the memory cells is erased at a time.
13. A method for erasing the nonvolatile semiconductor memory according to claim 9 , the method comprising:
applying a positive first voltage to all the bit lines and the source lines;
applying 0 V to a selected gate line;
applying a positive second voltage to a non-selected gate line; and
applying the positive first voltage to all the common source lines and the read lines, data of the memory cells connected to the selected gate line is erased at a time.
14. A method for erasing the nonvolatile semiconductor memory according to claim 9 , the method
applying a positive first voltage to a selected bit line and a selected source line;
applying a positive second voltage to a non-selected bit line and a non-selected source line, applying 0 V to all gate lines;
applying the positive second voltage to all the read lines; and
applying a positive third voltage which is half a sum of the positive first voltage and the positive second voltage to all the common source lines, data of the memory cells connected to the selected bit line is erased at a time.
15. A method for erasing the nonvolatile semiconductor memory according to claim 9 , the method comprising:
applying a positive first voltage to a selected bit line and a selected source line;
applying a positive second voltage to a non-selected bit line and a non-selected source line, applying 0 V to a selected gate line;
applying the positive second voltage to a non-selected control gate line;
applying the positive second voltage to the read lines; and
applying a positive third voltage which is half a sum of the positive first voltage and the positive second voltage to the common source lines, data of a selected memory cell is erased.