Method for fabricating semiconductor device

1. A method for fabricating semiconductor device, comprising:

providing a substrate;

forming a fin-shaped structure on the substrate and a shallow trench isolation (STI) around the fin-shaped structure;

forming a first gate structure on the substrate;

forming a first contact plug adjacent to the first gate structure and a second contact plug on the STI;

removing the second contact plug on the STI; and

performing a replacement metal gate (RMG) process to transform the first gate structure into metal gate after forming the first contact plug.

2. The method of claim 1 , further comprising:

forming the first gate structure on the substrate and a second gate structure on the STI, wherein the first gate structure comprises a first hard mask and the second gate structure comprises a second hard mask;

forming a first spacer adjacent to the first gate structure and a second spacer adjacent to the second gate structure;

forming a first contact plug contacting the first spacer and forming the second contact plug on the STI and contacting the second spacer;

forming a third hard mask on the first gate structure and the first contact plug;

removing the second contact plug to form a first recess;

forming an interlayer dielectric (ILD) layer in the first recess;

removing part of the first contact plug;

forming a fourth hard mask on the first contact plug; and

performing the RMG process.

3. The method of claim 2 , wherein the third hard mask and the fourth hard mask comprise same material.

4. The method of claim 2 , further comprising:

forming a source/drain region in the substrate and adjacent to the first gate structure;

forming silicide layer on the source/drain region;

forming a metal layer on the fin-shaped structure, the STI, the first gate structure, and the second gate structure; and

planarizing the metal layer to form the first contact plug and the second contact plug.

5. The method of claim 2 , wherein the RMG process further comprises:

removing the first gate structure and the second gate structure to form a second recess on the fin-shaped structure and a third recess on the STI;

forming a work function metal layer and a low resistance metal layer in the second recess and the third recess;

planarizing the low resistance metal layer and the work function metal layer to form a first metal gate on the fin-shaped structure and a second metal gate on the STI; and

forming a fifth hard mask on the first metal gate and a sixth hard mask on the second metal gate.

6. The method of claim 5 , wherein the top surfaces of the fourth hard mask and the fifth hard mask are coplanar.

7. The method of claim 5 , wherein the fourth hard mask and the fifth hard mask comprise different material.