Semiconductor device

1. A semiconductor device comprising:

a first interlayer insulating film, the first interlayer insulating film including a plug interlayer insulating film, and a bit-line interlayer insulating film provided on said plug interlayer insulating film, a plurality of bit-lines being formed between said plug interlayer insulating film and said bit-line interlayer insulating film, the plurality of bit-lines being covered with a bit-line insulating film disposed between the bit-line interlayer insulating film and the plug interlayer insulating film;

a second interlayer insulating film provided above the first interlayer insulating film;

a first conductive member provided lower than said first interlayer insulating film;

a contact plug comprising a single piece of conductor that includes a small-diameter part, and a large-diameter part arranged over said small-diameter part, an outer diameter of said large-diameter part being larger than an outer diameter of said small-diameter part, said contact plug penetrating through said first interlayer insulating film, and being electrically connected to said first conductive member, said large-diameter part of said contact plug having a top surface with a dented portion toward a bottom of said contact plug, the contact plug being arranged between adjacent bit-lines, at least part of the contact plug being located over a top surface of the bit-line insulating film over the bit-lines; and

a second conductive member that is provided on said first interlayer insulating film, and is electrically connected to said contact plug within said dented portion of said large-diameter part of said contact plug, the second conductive member having an outer diameter of a topmost edge of said second conductive member larger than an outer diameter of a bottom of said second conductive member, the second conductive member having side walls and the bottom extending therebetween, the side walls continuously narrowing and extending through the second interlayer insulating film to the first interlayer insulating film within the dented portion of the large-diameter part of the contact plug,

wherein the outer diameter of said large-diameter part is larger than the outer diameter of the bottom of said second conductive member, and

the outer diameter of the bottom of the second conductive member is larger than a diameter of the contact plug between adjacent bit-lines.

2. The semiconductor device according to claim 1 , wherein the outer diameter of said second conductive member increases from the bottom toward the topmost edge of said second conductive member.

3. The semiconductor device according to claim 2 , wherein a portion of said contact plug surrounds the bottom of said second conductive member.

4. The semiconductor device according to claim 2 , wherein said second conductive member comprises a different material from said contact plug.

5. The semiconductor device according to claim 2 , further comprising:

a third conductive member provided over said second conductive member; and

an insulating layer sandwiched between said second conductive member and said third conductive member.

6. A semiconductor device comprising:

a first interlayer insulating film, the first interlayer insulating film including a plug interlayer insulating film, and a bit-line interlayer insulating film provided on the plug interlayer insulating film, a plurality of bit-lines being formed between the plug interlayer insulating film and the bit-line interlayer insulating film, the plurality of bit-lines being covered with a bit-line insulating film disposed between the bit-line interlayer insulating film and the plug interlayer insulating film;

a second interlayer insulating film provided above the first interlayer insulating film;

a first conductive member provided lower than said first interlayer insulating film;

a contact plug formed inside a hole that penetrates through said first interlayer insulating film, and being electrically connected to said first conductive member, said contact plug comprising a single piece of conductor that includes a small-diameter part, and a large-diameter part arranged over said small-diameter part, an outer diameter of said large-diameter part being larger than an outer diameter of said small-diameter part, said large-diameter part of said contact plug having a top surface with a dented portion toward a bottom of said contact plug, the contact plug being arranged between adjacent bit-lines, at least part of the contact plug being located over a top surface of the bit-line insulating film over the bit-lines; and

a second conductive member that is provided on said first interlayer insulating film, and is electrically connected to said contact plug within said dented portion of said large-diameter part of said contact plug, the second conductive member having side walls and a bottom extending therebetween,

wherein an outer diameter of a topmost edge of said second conductive member is larger than an outer diameter of a bottom of said second conductive member, the outer diameter of said second conductive member continuously increasing from the bottom toward the topmost edge of said second conductive member, the side walls continuously narrowing and extending through the second interlayer insulating film to the first interlayer insulating film within the dented portion of the large-diameter part of the contact plug, and

the outer diameter of the bottom of the second conductive member is larger than a diameter of the contact plug between adjacent bit-lines.

7. The semiconductor device according to claim 6 , further comprising:

a third conductive member provided over said second conductive member; and

a second insulating layer sandwiched between said second conductive member and said third conductive member.

8. The semiconductor device according to claim 6 , wherein the outer diameter of said large-diameter part is smaller than the outer diameter of the topmost edge of said second conductive member.

9. A semiconductor device comprising:

a first interlayer insulating film comprising a plurality of insulating films including a first insulating film;

a second interlayer insulating film provided above the first interlayer insulating film;

a first conductive member provided lower than said first interlayer insulating film;

a contact plug formed inside a hole that penetrates through said first interlayer insulating film, and being electrically connected to said first conductive member, said contact plug comprising a single piece of conductor that includes a small-diameter part, and a large-diameter part arranged over said small-diameter part, an outer diameter of said large-diameter part being larger than an outer diameter of said small-diameter part, a plurality of bit-lines being provided between the contact plug and the first conductive member, the plurality of bit-lines being covered with a bit-line insulating film, at least part of the contact plug being located over a top surface of the bit-line insulating film over the bit-lines; and

a second conductive member that is provided on said first interlayer insulating film, and is electrically connected to said contact plug, the second conductive member having side walls and a bottom extending therebetween, a contact face between the bottom of said second conductive member and a top surface of said large-diameter part of said contact plug being lower in position than a top surface of said first insulating film, and upper in position than a bottom surface of said first insulating film, the side walls continuously narrowing and extending through the second interlayer insulating film to the first interlayer insulating film,

wherein an outer diameter of a topmost edge of said second conductive member is larger than an outer diameter of a bottom of said second conductive member, the outer diameter of said second conductive member continuously increasing from the bottom toward the topmost edge of the second conductive member, and

the outer diameter of the bottom of the second conductive member is larger than a diameter of the contact plug between adjacent bit-lines.

10. The semiconductor device according to claim 9 , further comprising:

a third conductive member provided over said second conductive member; and

a second insulating layer sandwiched between said second conductive member and said third conductive member.

11. The semiconductor device according to claim 9 , wherein:

said first interlayer insulating film includes a plug interlayer insulating film, and the bit-line insulating film provided on said plug interlayer insulating film, the plurality of bit-lines being formed between said plug interlayer insulating film and said bit-line insulating film, and

said contact plug is arranged between adjacent bit-lines.

12. The semiconductor device according to claim 9 , wherein the outer diameter of said large-diameter part is smaller than an outer diameter of the topmost edge of said second conductive member.

13. The semiconductor device according to claim 9 , wherein said second conductive member comprises a different material from said contact plug.