| 摘要 |
PURPOSE: To prevent leakage of electrons in a floating gate by forming a part being brought into contact with a tunnel film in the floating gate by a P type, and by allowing the electron accumulated in the floating gate to exist in an N-type region which is kept away from the tunnel film. CONSTITUTION: On a silicon substrate 101, a field oxide film 102 is formed, and then a tunnel oxide film 103 is formed. At this time, gas such as N2O is mixed to prevent boron from going through, and the tunnel film is formed by a nitride oxide film. Polysilicon 104 which becomes a floating gate is deposited on the oxide film. Then, boron ions are implanted (105), the entire floating gate is set as a P-type, and then phosphor ions are implanted (106). Then, the polysilicon 104 which becomes the floating gate is set as a double- layer structure of a P-type 108 in contact with the tunnel film and an N-type region 107 on the P-type. After then, polysilicon is etched forming a floating gate 109.
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