Semiconductor memory device of open bit line type

Abstract

There is provided a semiconductor memory device that includes: a plurality of memory mats each including a plurality of word lines, a plurality of bit lines, a plurality of memory cells each located at an intersection between the word line and the bit line, and at least one dummy word line not having connection to a dummy cell; a plurality of sense amplifier arrays located between adjacent memory mats, the sense amplifier arrays including a plurality of sense amplifiers including a pair of input/output nodes, one of which pair is connected to the bit lines of the adjacent memory mats on one side and the other of which pair is connected to the bit lines of the adjacent memory mats on the other side, respectively; and an activating unit which, in response to activation of the word line in a memory mat selected from the memory mats, activates the dummy word line in the memory mat adjacent to the selected memory mat.

What is claimed is: 
     
       1. A semiconductor memory device comprising:
 a plurality of memory mats each including a plurality of word lines, a plurality of bit lines, a plurality of memory cells each located at an intersection between the word line and the bit line, one or more dummy cells, and at least one dummy word line not having connection to a any dummy cell in the mat; 
 a plurality of sense amplifier arrays located between adjacent memory mats, the sense amplifier arrays including a plurality of sense amplifiers including a pair of input/output nodes, one of which pair is connected to the bit lines of the adjacent memory mats on one side and the other of which pair is connected to the bit lines of the adjacent memory mats on the other side, respectively, and wherein in each memory mat, no two adjacent bit lines of the plurality of bit lines for the memory mat are coupled to the same sense amplifier; and 
 an activating unit which, in response to activation of the word line in a memory mat selected from the memory mats, activates the dummy word line in the memory mat adjacent to the selected memory mat. 
 
     
     
       2. The semiconductor memory device as claimed in  claim 1 , wherein the dummy word lines in the memory mats adjacent to both sides of the selected memory mat are respectively activated when memory mats other than the memory mats positioned at both ends are selected from the memory mats. 
     
     
       3. The semiconductor memory device as claimed in  claim 1 , wherein among the memory mats, the memory mats positioned at both ends are simultaneously selected, and the dummy word lines in the memory mats adjacent to the memory mats positioned at the both ends are respectively activated. 
     
     
       4. The semiconductor memory device as claimed in  claim 1 , wherein
 the memory mats include a first memory mat positioned at one end, a second memory mat adjacent to the first memory mat, a third memory mat positioned at the other end, and a fourth memory mat adjacent to the third memory mat, 
 the first memory mat and the third memory mat are simultaneously selected, and 
 when the first and third memory mats are selected, the activating unit activates both of the dummy word lines belonging to the second and fourth memory mats, when the second memory mat is selected, the activating unit activates the dummy word line belonging to the first memory mat without activating the dummy word line belonging to the third memory mat, and when the fourth memory mat is selected, the activating unit activates the dummy word line belonging to the third memory mat without activating the dummy word line belonging to the first memory mat. 
 
     
     
       5. The semiconductor memory device as claimed in  claim 1 , wherein the dummy word lines are located at an interval of every two of the word lines. 
     
     
       6. The semiconductor memory device as claimed in  claim 5 , wherein within the memory mats, a plurality of active region arrays aligned along a wiring direction of the word lines are arranged, and the dummy word lines are wired along an element isolation region located between adjacent active region arrays. 
     
     
       7. The semiconductor memory device as claimed in  claim 1 , wherein the memory mats further include an unused word line connected to a at least one of the one or more dummy cell cells, and the unused word line is fixed in an inactive state. 
     
     
       8. A semiconductor memory device comprising:
 a plurality of memory mats each including a plurality of word lines, a plurality of dummy word lines located at an interval of every two of the word lines, a plurality of bit lines intersecting each of the word line and each of the dummy word line, and a plurality of memory cells each located at an intersection of each of the word line and each of the bit line; 
 a plurality of sense amplifier arrays located between adjacent memory mats, the sense amplifier arrays including a plurality of sense amplifiers including a pair of input/output nodes, one of which pair is connected to the bit lines of the adjacent memory mats on one side and the other of which pair is connected to the bit lines of the adjacent memory mats on the other side, respectively, and wherein in each memory mat, no two adjacent bit lines of the plurality of bit lines for the memory mat are coupled to the same sense amplifier; and 
 an activating unit which, in response to activation of the word line in a memory mat selected from the memory mats, activates the dummy word line in the memory mat adjacent to the selected memory mat, wherein within the memory mats, a plurality of active region arrays aligned along a wiring direction of the word lines are arranged, and the dummy word lines are wired along an element isolation region located between the adjacent active region arrays. 
 
     
     
       9. The semiconductor memory device as claimed in  claim 8 , wherein the memory cell is located at each intersection of two of the adjacent bit lines and two of the adjacent word lines. 
     
     
       10. The semiconductor memory device as claimed in  claim 8 , wherein the bit lines are alternately connected to the sense amplifier arrays located on one adjacent side and the sense amplifier arrays located on the other adjacent side. 
     
     
       11. A semiconductor device comprising:
 a plurality of memory arrays each including a plurality of word lines and a plurality of bit lines intersecting each of the word lines, wherein every third word line is a dummy word line and the word lines other than the dummy word lines are active word lines, wherein for each memory array, no two adjacent bit lines of the plurality of bit lines are coupled to the same sense amplifier;   a plurality of memory cells each located at an intersection of a respective active word line and a respective bit line;   a plurality of word line drivers each connected to a respective active word line; and   one or more dummy word line drivers each connected to a respective dummy word line, wherein a plurality of dummy word lines not connected to the one or more dummy word line drivers are connected to a fixed potential,   wherein the device is configured such that upon the activation of a word line driver of a memory array of the plurality of memory arrays, a dummy word line driver of the one or more dummy word line drivers is activated in an adjacent memory array.   
     
     
       12. The semiconductor device as claimed in claim 11 wherein the fixed potential is a ground potential. 
     
     
       13. The semiconductor device as claimed in claim 11 wherein the fixed potential is a negative potential. 
     
     
       14. The semiconductor device as claimed in claim 11 further comprising an unused word line at each of two ends of each of the plurality of memory arrays and a plurality of memory cells each located at an intersection of a respective unused word line and a respective bit line. 
     
     
       15. The semiconductor device as claimed in claim 14 further comprising a plurality of word line drivers each connected to a respective unused word line. 
     
     
       16. The semiconductor device as claimed in claim 11 further comprising two unused word lines at each of two ends of each of the plurality of memory arrays and a plurality of memory cells each located at an intersection of a respective unused word line and a respective bit line. 
     
     
       17. The semiconductor device as claimed in claim 16 further comprising a plurality of word line drivers each connected to a respective unused word line. 
     
     
       18. The semiconductor device as claimed in claim 11 further comprising a plurality of sense amplifiers located between adjacent memory arrays. 
     
     
       19. The semiconductor device as claimed in claim 18 wherein each of the plurality of sense amplifiers is connected to a respective bit line of one of the adjacent memory arrays and a respective bit line of another of the adjacent memory arrays. 
     
     
       20. The semiconductor device as claimed in claim 18 further comprising a potential supply circuit located at one side of memory arrays not having an adjacent memory array on the one side and connected to bit lines not connected to a sense amplifier. 
     
     
       21. The semiconductor device as claimed in claim 20 wherein the potential supply circuit supplies a precharge potential to the bit lines not connected to a sense amplifier. 
     
     
       22. The semiconductor device as claimed in claim 11 wherein the plurality of memory arrays are open bit line memory arrays.