Non-Volatile Semiconductor Memory Device Adapted to Store a Multi-Valued Data in a Single Memory Cell

A non-volatile semiconductor memory device comprising:

• a memory cell;
• a word line connected to a control gate of the memory cell;
• and
• a control circuit configured to control a voltage applied to the word line when a write operation is performed,
• wherein the write operation includes a plurality of loops each including:
• at least one program operation;
• and
• at least one verify operation subsequent to the program operation, wherein at least one of the loops includes:
• a program operation to increase a threshold voltage of the memory cell;
• a first verify operation to detect whether or not the threshold voltage of the memory cell reaches a first threshold value;
• and
• a second verify operation to detect whether or not the threshold voltage of the memory cell reaches a second threshold value, which is higher than the first threshold value.