In a non-volatile semiconductor memory device according to the present invention, a p type source region and a p type drain region are formed in the surface of an n well. A floating gate electrode and a control gate electrode are formed on a channel region with a tunnel oxide film interposed therebetween....http://www.google.de/patents/US6172397?utm_source=gb-gplus-sharePatent US6172397 - Non-volatile semiconductor memory device
