Non-volatile semiconductor memory

A non-volatile semiconductor memory in which a plurality of flash memory cells are arranged in a matrix, each flash memory cell comprising:

• source and drain regions in a silicon substrate;
• a floating gate overlapping at least a part of the source and drain regions, with a first dielectric film between the floating gate and the substrate;
• and
• a control gate on the floating gate, with a second dielectric layer between the control gate and the floating gate,
• a common source line connecting the source regions of the flash memory cells includes a diffusion layer formed in the silicon substrate and a silicide formed on the diffusion layer, and
• impurity concentration levels of the source region and the common source line are lower than an impurity concentration level of the drain region;
• wherein, during a writing operation, an FN (Fowler-Nordheim) tunnel current forms between the floating gate and the drain region upon application of a positive voltage to the drain region and of a negative voltage to the control gate to move electrons from the floating gate to the drain region, and
• wherein, during an erasing operation, FN tunnel current is formed between the drain region and the floating gate upon application of a negative voltage to the drain region, a negative voltage to the substrate, and a positive voltage to the control gate to move electrons from the drain region to the floating gate.