Semiconductor device and method of manufacturing the same
An insulating film made of the same material as that of a gate insulating film is formed so as to cover one sidewall of a control gate on a conducting film for floating gate. By selectively removing the conducting film for floating gate with the insulating film as a mask, a floating gate is formed from the conducting film for floating gate, and a portion of the gate insulating film is exposed at the floating gate. A nitrogen introduced portion is formed by introducing nitrogen into the exposed portion of the gate insulating film. Then, the insulating film is removed to expose an upper surface of a lateral protrusion of the floating gate. An erase gate is formed so as to face the upper surface and a side surface of the lateral protrusion.
1. A semiconductor device comprising:
a semiconductor substrate having a main surface;
a gate insulating film formed on the main surface of the semiconductor substrate;
a floating gate formed on the gate insulating film;
a control gate formed on the floating gate with a first insulating film interposed therebetween; and
an erase gate formed on the main surface,
the floating gate including a lateral protrusion protruding laterally from a region immediately below the control gate,
the erase gate being formed so as to face the lateral protrusion,
the gate insulating film including a first gate insulating portion located between the semiconductor substrate and the floating gate, and a second gate insulating portion located between the semiconductor substrate and the erase gate,
the second gate insulating portion having a portion made of a material different from that of the first gate insulating portion.
2. The semiconductor device according to claim 1 , wherein
the first gate insulating portion includes a portion made of silicon oxide, and the second gate insulating portion includes a portion made of silicon oxynitride.
3. The semiconductor device according to claim 1 , further comprising a select gate formed on the main surface of the semiconductor substrate, wherein
the gate insulating film includes a third gate insulating portion located between the semiconductor substrate and the select gate, and
the third gate insulating portion has a portion made of a material different from that of the first gate insulating portion.
4. The semiconductor device according to claim 3 , wherein
the third gate insulating portion includes a portion made of silicon oxynitride.