Semiconductor device including transistor with composite gate structure and transistor with single gate structure, and method for manufacturing the same
View Patent ↗A semiconductor device comprises a first transistor having a composite gate structure containing a lamination of a first polycrystalline silicon film, an interlayer insulating film, and a second polycrystalline silicon film; and a second transistor having a single gate structure containing a lamination of a third polycrystalline silicon film and a fourth polycrystalline silicon film, wherein the first polycrystalline silicon film and the third polycrystalline silicon film have substantially the same thickness; the first polycrystalline silicon film and the third polycrystalline silicon film have different impurity concentrations controlled independently of each other; the second polycrystalline silicon film and the fourth polycrystalline silicon film have substantially the same thickness, and the second polycrystalline silicon film, the fourth polycrystalline silicon film, and the third polycrystalline silicon film have substantially the same impurity concentration. Also, a method for manufacturing the above-described semiconductor device is described.
1. A semiconductor device, comprising:
a memory transistor having a composite gate structure containing a first conductive film, a first insulating film, and a second conductive film that overlie a first channel region, wherein said first conductive film is disposed closer to said first channel region than said second conductive film; and
a peripheral transistor having a single gate structure containing a third conductive film and a fourth conductive film that overlie a second channel region and are in contact over their cross-sections, wherein said third conductive film is disposed closer to said second channel region than said fourth conductive film;
wherein said second, third, and fourth conductive films each have a conductivity that is substantially the same and that is higher than a conductivity of said first conductive film.
2. The semiconductor device of claim 1 , wherein said first conductive film and said third conductive film have substantially the same thickness.
3. The semiconductor device of claim 2 , wherein said second conductive film and said fourth conductive film have substantially the same thickness.
4. The semiconductor device of claim 3 , wherein said second conductive film, said third conductive film, and said fourth conductive film have an impurity concentration that is substantially the same and that is at least 10 times an impurity concentration of said first conductive film.
5. The semiconductor device of claim 1 , wherein an impurity concentration of said first conductive film is between 1×10 18 and 1×10 19 atoms/cm 3 .
6. The semiconductor device of claim 5 , wherein an impurity concentration of said third conductive film is between 1×10 20 and 1×10 21 atoms/cm 3 .
7. The semiconductor device of claim 6 , wherein an impurity concentration of said second conductive film is between 1×10 20 and 1×10 21 atoms/cm 3 .
8. The semiconductor device of claim 7 , wherein an impurity concentration of said fourth conductive film is between 1×10 20 and 1×10 21 atoms/cm 3 .
9. The semiconductor device of claim 1 , wherein said first, second, third, and fourth conductive films are polycrystalline silicon films.
10. The semiconductor device of claim 1 , wherein said first insulating film is a silicon oxide/silicon nitride/silicon oxide (ONO) film.
11. The semiconductor device of claim 1 , wherein said first conductive film is doped with phosphorous.
12. The semiconductor device of claim 1 , wherein said first conductive film is doped with arsenic.
13. The semiconductor device of claim 1 , wherein the semiconductor device is an EEPROM.
14. The semiconductor device of claim 1 , wherein the semiconductor device is an EPROM.
15. The semiconductor device of claim 1 , wherein said second, third, and fourth conductive films have substantially the same resistance.
16. A semiconductor device, comprising:
a memory transistor having a composite gate structure containing a first conductive film, a first insulating film, and a second conductive film that overlie a substrate, wherein said first conductive film is separated from said substrate by a tunnel oxide layer, and wherein said first conductive film is separated from said second conductive film by said first insulating film; and
a peripheral transistor having a single gate structure containing a third conductive film and a third conductive film that overlie said substrate, wherein said fourth conductive film is on top of said third conductive film, and wherein said third and fourth conductive films are in contact over their cross-sections;
wherein said second, third, and fourth conductive films each have a conductivity that is substantially the same and that is higher than a conductivity of said first conductive film.
17. The semiconductor device of claim 16 , wherein a gate oxide film and a field oxide film are between said substrate and said third conductive film.
18. The semiconductor device of claim 16 , wherein said second conductive film, said third conductive film, and said fourth conductive film have an impurity concentration that is substantially the same and that is at least 10 times an impurity concentration of said first conductive film.