1. A semiconductor device comprising:
a semiconductor substrate including an upper surface;
an insulating film formed above the upper surface of the semiconductor substrate, the insulating film including a contact hole penetrating the insulating film to expose the first upper surface, the contact hole including an upper portion and a lower portion located on the upper portion via a boundary portion as a first lower end of the upper portion and a first upper end of the lower portion, the upper portion including a second upper end having a first inner width, the boundary portion including a second inner width being same as the first inner width, and the lower portion including a second lower end having a third inner width being narrower than the second inner width;
a first conductive plug made from polycrystalline silicon and formed in the lower portion of the contact hole so that the exposed upper surface of the semiconductor substrate is in contact with the first conductive plug; and
a second conductive plug formed on the first conductive plug, and the second conductive plug being made from a conductive material which is different from the polycrystalline silicon.
2. The semiconductor device according to claim 1, wherein the first and second conductive plugs have therebetween an interface with a height lower than a height of the boundary portion of the contact hole relative to the upper surface of the semiconductor substrate.
3. The semiconductor device according to claim 1, wherein the second conductive plug is formed into a metal plug provided with a tungsten layer.
4. The semiconductor device according to claim 1, wherein the second conductive plug includes a barrier metal film and a tungsten layer located inside of the barrier metal film.
5. The semiconductor device according to claim 1, wherein the insulating film includes a first inner side wall facing to the upper portion of the contact hole, and the first inner side wall is formed vertically relative to the upper surface of the semiconductor substrate.
6. The semiconductor device according to claim 5, wherein the insulating film includes a second inner side wall facing to the lower portion of the contact hole, and the second inner side wall has a tapered portion relative to the first inner side wall.
7. The semiconductor device according to claim 1, wherein the semiconductor substrate includes an impurity diffusion layer which contact to the first conductive plug.
8. The semiconductor device according to claim 1, further comprising a silicon nitride film between the upper surface and the insulating film.
9. The semiconductor device according to claim 1, further comprising an element isolation insulating film embedded in the upper surface of the semiconductor substrate and a silicon nitride film formed between the element isolation film and the insulating film.
10. A semiconductor device comprising:
a semiconductor substrate including an upper surface;
an insulating film formed above the upper surface of the semiconductor substrate, the insulating film including a contact hole penetrating the insulating film to expose the first upper surface, the contact hole including an upper portion and a lower portion located on the upper portion via a boundary portion as a first lower end of the upper portion and a first upper end of the lower portion, the upper portion including a second upper end having a first inner width, the boundary portion including a second inner width being same as the first inner width, and the lower portion including a second lower end having a third inner width being narrower than the second inner width;
a first conductive material including a first filling property and formed in the lower portion of the contact hole so that the exposed upper surface of the semiconductor substrate is contact to the first conductive plug; and
a second conductive material including a second filling property being worse than the first filling property of the first conductive plug and formed on the first conductive plug.
11. The semiconductor device according to claim 10, wherein the first conductive material includes polycrystalline silicon.
12. The semiconductor device according to claim 11, wherein the second conductive material includes a metal layer.
13. The semiconductor device according to claim 12, wherein the second conductive material includes a tungsten layer.
14. A method of fabricating a semiconductor device, comprising:
forming an insulating film on an upper surface of a semiconductor substrate;
forming a contact hole in the insulating film to expose the upper surface so that the contact hole includes an upper portion, a lower portion and a boundary portion located between the upper and the lower portions, the upper portion has a first inner width, the boundary portion has a second inner width which is same as the first inner width of the upper portion, the lower portion has a third inner width which is smaller than the second inner width of the boundary portion;
forming a first conductive plug from the exposed upper surface of the semiconductor substrate to a first level which is lower than a second level of the boundary portion relative to the upper surface of the semiconductor substrate; and
forming a second conductive plug which is different from the first conductive plug on the first conductive plug.
15. The method according to claim 14, wherein the contact hole formed by a reactive ion etching (RIE) using an oxide gas and a fluorocarbon gas.
16. The method according to claim 15, wherein the contact hole forming step includes a change step which changes a condition of a flux of the oxide gas and the fluorocarbon gas.
17. The method according to claim 14, wherein the second plug forming step includes a first step of forming a barrier film and a second step of forming a metal film.
18. The method according to claim 14, further comprising a step of forming an impurity diffusion layer, which contact to the first conductive plug, in the upper surface of the semiconductor substrate.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for enhancing the deposit resistance of lubricating oil composition used under sustained high load conditions comprising adding to a Group II base stock oil a combination of additives comprising a minor amount of detergent comprising: i) a low TBN calcium alkyl salicylate a low TBN calcium phenate or combinations thereof at from 2.2 to 6.3 vol. % and optional overbased calcium phenate at from 0.3 to 0.5 vol. %, ii) at least two of the three of a phenolic antioxidant, a functionalized glycerine derivative with a grafted hindered phenolic moiety and a hindered phenolic containing a thioether group, wherein the phenolic antioxidant is at from about 0.75 to 2.0 vol. %, the functionalized glycerine derivative with a grafted hindered phenolic moiety is at from 0.50 to 3.0 vol. % and the hinder phenolic containing a thioether group is at from about 0.5 to 3 mass % active ingredient based on the weight of the lubricating oil composition, and iii) an organomolybdenum complex comprising molybdenum dithiocarbamate present in an amount sufficient to provide about 25 wppm to about 2000 wppm elemental molybdenum.
2. The method of claim 1 wherein the base stock oil has a kinematic viscosity at 100\xb0 C. of about 5 to about 20 mm2s.
3. The method of claim 1 wherein the base stock oil has a kinematic viscosity at 100\xb0 C. of about 5 to about 16 mm2s.
4. The method of claim 1 wherein the base stock oil has a kinematic viscosity at 100\xb0 C. of about 9 to about 13 mm2s.
5. The method of claim 1, 2, 3 or 4 wherein the low TBN calcium alkyl salicylate and low TBN calcium phenate detergent has a TBN of about 114 mg KOHg or less and the optional overbased calcium phenate detergent has a TBN of about 250 mg KOHg or more.
6. The method of claim 1 wherein the organo molybdenum complex is present in an amount sufficient to provide about 50 wppm to about 500 wppm elemental molybdenum.
7. The method of claim 1, 2, 3 or 4 wherein the lubricating oil composition further includes about 0.5 vol. % of neutral calcium sulphonate detergent.
8. The method of claim 1, 2, 3 or 4 wherein the lubricating oil composition additionally contains one or more other additives comprising antioxidants, viscosity index improvers, pour point depressants, antiwearextreme pressure additives, antifoamants, dyes, metal deactivators, additional detergents, dispersants.
9. The method of claim 1, 2, 3 or 4 wherein the lubricating oil composition is a stationary gas engine oil, stationary diesel engine oil, locomotive diesel engine oil, marine diesel engine oil.
10. The method of claim 8 wherein the one or more other additives are ashless additives.