A nonvolatile memory, such as a write-once memory, includes a memory cell
array that has first memory cells and at least one second memory cell.
The memory also includes a first writing circuit that is capable of
writing data to the first memory cells and the second memory cell, a
second writing circuit, and a verify circuit which is capable of
confirming whether the data is normally stored in the first memory cells.
When the writing of data to one of the first memory cells fails, the
second writing circuit is arranged to assign an address of the one of the
first memory cells to the second memory cell. The first memory cells and
the second memory cell are arranged to irreversibly change their
electrical resistance when the data is stored in them. The first memory
cells and the second memory cell include an organic compound layer
interposed between a pair of electrodes.