Nonvolatile semiconductor memory device having improved redundancy relieving rate
View Patent ↗In a memory cell array of an MRAM, a normal memory cell is compared with a reference memory cell which holds a reference value, thereby storing data of one bit per cell. Two spare memory cells store data of one bit as a whole. By writing complementary values to the two spare memory cells and connecting these spare memory cells to a sense amplifier, the stored data of one bit is read. A spare memory cell section which is often arranged in an array peripheral portion becomes more resistant against a variation in finished dimensions of elements and a success rate for replacing and relieving a defective memory cell by a spare memory cell increases.
1. A nonvolatile semiconductor memory device comprising:
a plurality of normal memory cells each storing data of one bit in a nonvolatile mannner;
a plurality of spare memory cells each used in place of a defective memory cell when the defective memory cell is present in said plurality of normal memory cells, and constituted so that two spare memory cells store data of one bit as a whole;
a control circuit, in accordance with an external access, selecting a first memory cell group corresponding to an address signal from among said plurality of normal memory cells and selecting a second memory cell group from among said plurality of spare memory cells in parallel to selection of said first memory cell group; and
a select and amplification section selecting a read memory cell group in accordance with said address signal from among said first and second memory cell groups, and amplifying and outputting the data held in said read memory cell group, wherein
said plurality of normal memory cells are arranged in rows and columns, and
said nonvolatile semiconductor memory device further comprising:
a plurality of word lines provided along said rows of said plurality of normal memory cells;
a plurality of bit lines provided along said columns of said plurality of normal memory cells;
a plurality of reference memory cells provided adjacent to a region in which said plurality of normal memory cells are arranged, arranged to form columns along a column direction of said plurality of normal memory cells, and each holding a reference value for determining a read value when the data is read from each of said normal memory cells;
first and second data lines, one of the first and second data lines being connected to one of said plurality of normal memory cells and the other being connected to one of said plurality of reference memory cells; and
third and fourth data lines connected to first and second spare memory cells, among said plurality of spare memory cells, forming a pair and storing predetermined data of one bit as the pair.
2. A nonvolatile semiconductor memory device comprising:
a plurality of normal memory cells each storing data of one bit in a nonvolatile manner;
a plurality of spare memory cells each used in place of a defective memory cell when the defective memory cell is present in said plurality of normal memory cells, and constituted so that two spare memory cells store data of one bit as a whole;
a control circuit, in accordance with an external access, selecting a first memory cell group corresponding to an address signal from among said plurality of normal memory cells and selecting a second memory cell group from among said plurality of spare memory cells in parallel to selection of said first memory cell group; and
a select and amplification section selecting a read memory cell group in accordance with said address signal from among said first and second memory cell groups, and amplifying and outputting the data held in said read memory cell group, wherein
said plurality of normal memory cells are arranged in rows and columns, and
said nonvolatile semiconductor memory device further comprising:
a plurality of digit lines each provided corresponding to each of said rows of said plurality of normal memory cells; and
a plurality of word lines, two word lines provided corresponding to each of said rows of said plurality of normal memory cells, for selecting the rows during data read,
said plurality of normal memory cells in each row are alternately connected to corresponding two of said word lines, and
said nonvolatile semiconductor memory device further comprising:
a plurality of reference memory cells provided adjacent to a region in which said plurality of normal memory cells are arranged, arranged to form rows along a row direction of said plurality of normal memory cells, and each holding a reference value for determining a read value when reading the data from each of said normal memory cells.