Variable capacity semiconductor memory device
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsShinichi Kobayashi, Yoshihide Kai
Life of this patent
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Abstract
The invention provides a semiconductor memory capable of realizing an efficient use of a memory area and reducing manufacturing costs. A memory has a memory cell array comprising a matrix of cells for electrically storing data. The memory cell array is divided into a plurality of block areas. Each block area is set to a four-valued area for recording the data as four-valued data or a binary area for recording the data as binary data. On an access to a memory cell (writing or reading of the data), a word line voltage for writing or a sense amplifier for reading is switched in accordance with whether the data to be accessed is the binary data or the four-valued data.
Claims16
A nonvolatile semiconductor memory device capable of electrical data writing and data reading, comprising:
- a memory cell array comprising a plurality of memory cells and having a data storing area divided into a plurality of areas, each of the divided areas selectively being set to a binary area for storing binary data or a multivalued area for storing multivalued data;
- a word line driver for supplying a driving voltage to a word line of the memory cell array;
- a voltage controller for controlling an output voltage of the word line driver;
- and
- a binary/multivalued controller for controlling the voltage controller so as to switch the output voltage of the word line driver in accordance with whether the data is to be recorded to the cell in the form of the binary data or the multivalued data.
A nonvolatile semiconductor memory device capable of electrically writing and reading data, comprising:
- a memory cell array comprising a plurality of memory cells and having a data storing area divided into a plurality of areas, each of the divided areas selectively being set to a binary area for storing binary data or a multivalued area for storing multivalued data;
- a binary sense amplifier to be used when the binary data is read out from the memory cell;
- a multivalued sense amplifier to be used when the multivalued data is read out from the memory cell;
- and
- a binary/multivalued controller for selecting, as a sense amplifier to be used in data reading, the binary sense amplifier when the data is read from the binary area, or the multivalued sense amplifier when the data is read from the multivalued area.
Dependencies are inferred from the claim text.