Semiconductor memory device and a method for producing the same

A method for producing a semiconductor memory device comprising the steps of:

• forming a first insulating film on a conductive silicon substrate in which a plurality of reverse conductive wells and a plurality of element separation regions are formed;
• forming a first polysilicon layer on the first insulating film;
• patterning the first polysilicon layer to form a floating gate electrode layer of a non-volatile memory element and a transistor gate electrode layer with a breakdown-voltage of 20 V or less;
• forming a second insulating film on the silicon substrate;
• forming a second polysilicon layer on the second insulating film;
• patterning the second polysilicon layer to form a logic electrode layer, a transfer gate electrode layer of a volatile memory element, a driver electrode layer, and a control gate electrode layer of a non-volatile memory element;
• forming a third insulating film on the silicon substrate;
• forming a third polysilicon layer on the third insulating film;
• and
• patterning the third polysilicon layer to form a charge storage electrode layer of a volatile memory element so that the charge storage electrode layer is partly disposed on the transfer gate electrode layer with the third insulating film sandwiched there-between.