NONVOLATILE SEMICONDUCTOR STORAGE DEVICE AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor storage device which has a high gate coupling ratio needed for writing/erasing using an FN current without causing characteristic defects due to short-channel effect. SOLUTION: After a control gate of a memory cell is formed, a side wall spacer of a silicon nitride film is formed on the side wall of the control gate and then thermally oxidized to prevent a floating gate upper part which is in contact with an insulating film between the control gate and floating gate from being oxidized; and the silicon substrate below the floating gate which is in contact with a tunnel gate oxide area is oxidized to provide the nonvolatile semiconductor storage device.