Method for fabricating semiconductor device including silicon-containing layer and metal-containing layer, and conductive structure of the same

1. A method for fabricating a semiconductor device, comprising:

forming an interlayer dielectric layer over a semiconductor substrate;

forming a contact hole by etching the interlayer dielectric layer;

forming a preliminary plug filling the contact hole, wherein the preliminary plug includes a silicon-containing layer;

selectively etching back the silicon-containing layer; and

forming an undercut prevention layer formed over the etched back silicon-containing layer;

forming a metal-containing layer over the interlayer dielectric layer including the preliminary plug; and

forming a bit line and a bit line contact plug by etching the metal-containing layer and the preliminary plug.

2. The method of claim 1 , wherein the undercut prevention layer comprises chemical species for controlling an etch rate.

3. The method of claim 1 , wherein the undercut prevention layer comprises at least one of carbon and nitrogen.

4. The method of claim 1 , wherein a first polysilicon layer is formed as the silicon-containing layer, and a second polysilicon layer containing at least one of carbon and nitrogen is formed as the undercut prevention layer over the first polysilicon layer.

5. The method of claim 4 , wherein the first and second polysilicon layers comprise N-type or P-type impurities.

6. The method of claim 1 , wherein a polysilicon layer is formed as the silicon-containing layer, and the undercut prevention layer is formed by injecting at least one of carbon and nitrogen into an upper part of the polysilicon layer.

7. The method of claim 6 , wherein the polysilicon layer comprises N-type or P-type impurities.

8. The method of claim 1 , wherein the forming of the metal-containing layer comprises:

forming a tungsten-based metal barrier; and

forming a tungsten-based metal layer over the tungsten-based metal barrier.