Editing EEPROM (section)

==Failure modes==
There are two limitations of stored information: endurance and data retention.

During rewrites, the gate oxide in the [[floating-gate transistor]]s gradually accumulates trapped electrons. The electric field of the trapped electrons adds to the electrons in the floating gate, lowering the window between threshold voltages for zeros vs ones. After sufficient number of rewrite cycles, the difference becomes too small to be recognizable, the cell is stuck in programmed state, and endurance failure occurs. The manufacturers usually specify the maximum number of rewrites being 1 million or more.<ref>{{cite web|url=http://www.rohm.com/products/lsi/eeprom/faq.html|title=Frequently Asked Questions -ROHM Semiconductor|url-status=live|archive-url=https://web.archive.org/web/20110219060902/http://www.rohm.com/products/lsi/eeprom/faq.html|archive-date=2011-02-19}}</ref>

During storage, the electrons injected into the floating gate may drift through the insulator, especially at increased temperature, and cause charge loss, reverting the cell into erased state. The manufacturers usually guarantee data retention of 10 years or more.<ref>System Integration - From Transistor Design to Large Scale Integrated Circuits</ref>