| 摘要 |
A semiconductor memory device having at least one floating gate includes a semiconductor substrate; at least one device-isolation region buried in the semiconductor substrate, having a top surface protruding from a top surface of the semiconductor substrate, the top surface of the device-isolation region having a concave section that has a depression thereon; at least one gate-insulating film formed on the semiconductor substrate; a first gate formed on the gate-insulating film, the device-isolation region and the depression; a gate-to-gate insulating film formed on the first gate and in the concave section and the depression of the device-isolation region; and a second gate formed on the gate-to-gate insulation film, the depression being filled with the second gate. A method of producing a semiconductor memory device having floating gates, forms at least one device-isolation region and a gate-insulating film on a semiconductor substrate; forms a first gate material on the device-isolation region and the gate-insulating film; forms first gate electrodes by separating the first gate material into two gate materials, the separated materials being left on the device-isolation region; provides a concave section on the device-isolation region, the concave section being narrower than a distance between the separated first gate electrodes; provides a depression in the device-isolation region under the first gate electrodes and at edges of the concave section on the device-isolation region; forms a gate-to-gate insulating film on the concave section on the device-isolation region and the first gate electrodes, the depression in the device-isolation region being filled with the gate-to-gate insulating film; and forms a second gate electrode on the gate-to-gate insulation film.
|
