Interconnection structure including air gap, semiconductor device including air gap, and method of manufacturing the same

1. A semiconductor device comprising:

a first insulating layer;

a second insulating layer formed on the first insulating layer;

a first air gap disposed between the first insulating layer and the second insulating layer; and

a plurality of interconnection lines formed in the second insulating layer,

wherein a lower part of the interconnection lines protrudes into the first air gap and is surrounded by the first air gap,

wherein a height of the first air gap is less than a height of the interconnection lines, and a space between the interconnection lines above the first air gap is filled with the second insulating layer.

2. The semiconductor device of claim 1 , further comprising:

a plurality of second air gaps each disposed within the second insulating layer between the interconnection lines.

3. The semiconductor device of claim 2 , wherein each of the plurality of second air gaps are separated from the first air gap by the second insulating layer.

4. The semiconductor device of claim 1 , further comprising a dummy contact plug extending to the first air gap through the second insulating layer.

5. The semiconductor device of claim 1 , wherein the interconnection lines are bit lines.

6. The semiconductor device of claim 1 , further comprising:

conductive layers and insulating layers, which are alternately stacked and positioned under the first insulating layer; and

a plurality of channel layers connected to the interconnection lines through the conductive layers and insulating layers.

7. The semiconductor device of claim 1 , further comprising a plurality of contact plugs formed in the first insulating layer and connected to the interconnection lines.

8. An interconnection structure comprising:

an insulating layer including a plurality of interconnection lines therein;

a first air gap defined in the insulating layer and positioned between lower portions of the interconnection lines; and

a plurality of second air gaps defined in the insulating layer and positioned between the interconnection lines,

wherein the lower portions of the interconnection lines are surrounded by the first air gap,

wherein a height of the first air gap is less than a height of the interconnection lines.

9. The interconnection structure of claim 8 , further comprising:

a dummy contact plug extending to the first air gap through the insulating layer.

10. The interconnection structure of claim 8 , further comprising:

a plurality of contact plugs connected to lower portions of the interconnection lines through the insulating layer.

11. The interconnection structure of claim 8 , wherein each of the second air gaps are separated from the first air gap by the insulating layer.