Nonvolatile semiconductor storage device
AssigneeRohm Co., Ltd.
InventorsNoriaki Katsuhara, Yoshihiro Tada, Hiromi Uenoyama
Life of this patent
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Abstract
The same information is stored in two memory cells (26 and 26′) and the two memory cells are connected in parallel (OR) at a normal reading to synthesize an electric current in conformity with information in the two memory cells. Even if a floating gate and drain are shorted with each other in a storage transistor in one of the memory cells when a tunnel oxide film is deteriorated, destroyed or shorted by a high-tension stress, the discriminating voltage of a sense amplifier is determined so as to ensure normal reading of information in the other memory cell. The two memory cells are separated at test-reading for independent operations to ensure individual testing each memory cell.
Claims6
A non-volatile semiconductor memory device comprising:
- a plurality of memory cells each connected to a bit line and a word line, the memory cells including a plurality of first memory cells and a plurality of second memory cells each corresponding to a first memory cell;
- and
- control means for storing the same information in the corresponding first and second memory cells and reading the information stored in the corresponding first and second memory cells by synthesizing the current into the first and second memory cells in a first mode and reading independently the information stored in the first and second memory cells in a second mode.
Dependencies are inferred from the claim text.