Nonvolatile semiconductor storage device

摘要

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.