Patent ID: 8270220

Claim:
A nonvolatile semiconductor storage device comprising: a memory cell array comprising a plurality of active areas extending in a first direction, a dummy active area extending in the first direction, a plurality of memory cells on the active areas, a plurality of first dummy cells on the dummy active area, a plurality of diffusion layer areas each connected to the corresponding memory cell and the corresponding first dummy cell, a plurality of first contacts in the respective active areas, and a second contact in the dummy active area; and a peripheral circuit comprising a threshold measuring unit and a voltage applying unit, wherein the threshold measuring unit measures a threshold of the first dummy cells, and the voltage applying unit applies a first voltage to set each of the memory cells in a program enable state or a second voltage to set the memory cells in a program inhibit state to each of the first contacts, and applies a third voltage to change the threshold of the first dummy cells to the second contact when the threshold measured by the threshold measuring unit is lower than a predetermined value.