Method for fabricating semiconductor device

1. A method for fabricating a semiconductor device having a capacitor of a metal-insulator-metal structure, comprising:

forming a polysilicon layer on a lower metal layer by plasma-enhanced chemical vapor deposition;

forming an uneven surface in the polysilicon layer by etching the polysilicon layer with an isotropic etchant;

forming an upper metal layer on the polysilicon layer;

sequentially etching the upper metal layer and the polysilicon layer; and

performing chemical-mechanical polishing after completing a gap-fill process on the upper metal layer.

2. The method of claim 1 , wherein forming the polysilicon layer is performed at a temperature between 350° C. and 400° C. and wherein the polysilicon layer has a thickness between 100 Å and 1000 Å.

3. The method of claim 1 , wherein forming the lower metal layer is performed by sequentially depositing a barrier metal, an aluminum layer, and a reflection-preventive layer.

4. The method of claim 3 , wherein the barrier metal is formed of Ti and the reflection-preventive layer is formed of TiN.

5. The method of claim 1 , wherein the isotropic etchant is any one of KOH, NaOH, and a compound formed by adding alcohol to one of KOH and NaOH.

6. The method of claim 1 , wherein, in forming an uneven surface, a surface of the polysilicon layer is transformed to Si x N y H z , using one of NH 3 plasma and N 2 plasma.

7. The method of claim 1 , wherein forming the upper metal layer is performed by sequentially depositing Ti/TiN, an aluminum layer, and Ti/TiN.

8. The method of claim 1 , wherein etching the upper metal layer and the polysilicon layer is performed with a plasma etching process using a photoresist pattern.