PURPOSE: To obtain a nonvolatile semiconductor memory in which an excess generated in production of a mask programable ROM for storing inherent data for a first customer is delivered as a product sample without leaking the data to a second customer.

CONSTITUTION: Data which is not inherent to a customer and formed arbitrarily at a memory maker side is stored in a redundant memory cell array 16. Only the cell of the array 16 is selected by melting a fuse of a fuse circuit 15. In this case, selection of the cell of a memory cell array 2 for storing the data at this time is inactivated to read only data formed arbitrary by the maker side from the array 2. A power source voltage is set to 5V, a higher voltage by about 5-7V than that is applied to a chip enable signal input terminal 11 and an output enable input terminal 10 to melt the fuse of the circuit 15.