Semiconductor device and method for manufacturing same
A semiconductor device includes a first well and a second well provided within a semiconductor substrate, an isolation region disposed between the first well and the second well within the semiconductor substrate, a first wiring disposed on the first well, a second wiring disposed on the second well, a concave third wiring disposed on the isolation region, a buried insulating film disposed on the third wiring so as to fill the concave portion thereof, a plurality of fourth wirings disposed on the buried insulating film, and a contact plug disposed so as to electrically connect to at least one of the first and second wells.
1. A method for manufacturing a semiconductor device, comprising:
preparing a semiconductor substrate including a first well, a second well, and an isolation region between the first well and the second well with respect to a first direction;
forming a first conductive film which is located on the first well and one end of which in the first direction is positioned on the isolation region, and a second conductive film which is located on the second well and one end of which in the first direction is positioned on the isolation region;
forming a third conductive film, so as to extend from a space on the first conductive film through a space on the isolation region to a space on the second conductive film with respect to the first direction, and have a concave shape on the isolation region;
forming a buried insulating film on the third conductive film, so as to fill a concave portion of the third conductive film on the isolation region;
patterning the first to third conductive films and the buried insulating film to form a first wiring on the first well, a second wiring on the second well, and a concave third wiring and a buried insulating film on the isolation region;
forming an interlayer insulating film on the semiconductor substrate;
removing a portion of the interlayer insulating film until the buried insulating film is exposed;
forming a contact plug, so as to penetrate through the interlayer insulating film, resulting in contacting with at least one of the first and second wells; and
forming a plurality of fourth wirings, so as to contact with the buried insulating film on the third wiring.
2. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the buried insulating film is formed by an ALD method or a low-pressure CVD method in forming the buried insulating film.
3. The method for manufacturing a semiconductor device according to claim 1 , further comprising forming a first insulating film by a plasma CVD method between forming the third conductive film and forming the buried insulating film.
4. The method for manufacturing a semiconductor device according to claim 1 , further comprising forming a second insulating film on the buried insulating film by a plasma CVD method, following forming the buried insulating film.
5. The method for manufacturing a semiconductor device according to claim 4 ,
wherein the second insulating film is removed in removing the portion of the interlayer insulating film.
6. The method for manufacturing a semiconductor device according to claim 1 , further comprising, between forming the first to third wirings and the buried insulating film and forming the interlayer insulating film:
forming a first source and drain on both sides of the first wiring within the first well; and
forming a second source and drain on both sides of the second wiring within the second well,
wherein a first transistor including the first source and drain and the first wiring as a first gate electrode is formed, and a second transistor including the second source and drain and the second wiring as a second gate electrode is formed.
7. The method for manufacturing a semiconductor device according to claim 6 ,
wherein the first transistor is an N-channel transistor, and the second transistor is a P-channel transistor.
8. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the first well, the second well and the isolation region are located in a peripheral circuit region of the semiconductor substrate,
the method further comprises:
forming a third transistor including a third source and drain in a memory cell region of the semiconductor substrate, between preparing the semiconductor substrate and forming the first to third wirings and the buried insulating film; and
forming a capacitor electrically connected to one of the third source and drain, following forming the fourth wirings.
9. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the first conductive film includes a first metal film and an impurity-containing polysilicon film in order from the side nearest to the semiconductor substrate, and
the second conductive film includes the first metal film and the impurity-containing polysilicon film in order from the side nearest to the semiconductor substrate.
10. The method for manufacturing a semiconductor device according to claim 9 ,
wherein the third conductive film includes the impurity-containing polysilicon film and a second metal film in order from the side nearest to the semiconductor substrate.