Fabrication method for semiconductor device having laminated electronic conductor on bit line
There are provided a semiconductor device and a fabrication method therefor including an ONO film ( 18 ) formed on a semiconductor substrate ( 10 ), a word line ( 24 ) formed on the ONO film ( 18 ), a bit line ( 20 ) formed in the semiconductor substrate ( 10 ), and a conductive layer ( 32 ) that is in contact with the bit line ( 20 ), runs in a length direction of the bit line ( 20 ), and includes a polysilicon layer or a metal layer. In accordance with the present invention, a semiconductor device and a fabrication method therefor are provided wherein degradation of the writing and erasing characteristics and degradation of the transistor characteristics such as a junction leakage are suppressed, and the bit line resistance is decreased.
1. A method of fabricating a semiconductor device comprising:
forming a tunnel oxide film and a trap layer overlaying the tunnel oxide film on a semiconductor substrate;
forming a bit line in the semiconductor substrate;
forming an opening in contact with the bit line in the tunnel oxide film and in the trap layer; and
forming a conductive layer in the opening and running in a length direction of the bit line, wherein the conductive layer runs substantially the entire length of the bit line, and wherein the conductive layer comprises a polysilicon layer or a metal layer in contact with the bit line.
2. The method as claimed in claim 1 , further comprising forming a protection film on the trap layer, wherein forming the opening includes forming the opening in the protection film.
3. The method as claimed in claim 2 , wherein forming the conductive layer includes:
forming the polysilicon layer or the metal layer on the protection film and in the opening; and
polishing the protection film and either the polysilicon layer or the metal layer.
4. The method as claimed in claim 3 , further comprising forming a metal silicide layer on the conductive layer.
5. The method as claimed in claim 4 , wherein forming the metal silicide layer includes forming a metal layer to be silicided on the conductive layer and on a silicon nitride film.
6. The method as claimed in claim 2 , further comprising:
removing the protection film; and
forming a top oxide film over the trap layer and the conductive layer.
7. The method as claimed in claim 6 , wherein forming the top oxide film comprises forming the top oxide film having a thickness less than that of the protection film.
8. The method as claimed in claim 6 , further comprising forming a word line on the top oxide film.
9. The method as claimed in claim 2 , further comprising forming a portion of an oxide film over the protection film and the conductive layer, wherein a top oxide film comprises the protection film and the portion of the oxide film.
10. The method as claimed in claim 1 , wherein forming the conductive layer includes:
forming the polysilicon layer or the metal layer in the opening and on the trap layer; and
etching the polysilicon layer or the metal layer in regions other than the opening.
11. The method as claimed in claim 10 , wherein a width of the conductive layer is greater than that of the tunnel oxide film and the trap layer.
12. The method as claimed in claim 10 , further comprising forming a metal silicide layer on the conductive layer.
13. The method as claimed in claim 1 , wherein forming the opening includes etching the trap layer and the tunnel oxide film by using a mask layer and sidewalls as an etching mask, wherein the mask layer is provided above the trap layer, and wherein the sidewalls are formed at both sides of an opening in the mask layer.