Method for fabricating semiconductor device

A method for fabricating semiconductor device, comprising:

• providing a substrate having a first region and a second region defined thereon;
• forming a plurality of fin-shaped structures on the substrate;
• forming a gate layer on the fin-shaped structures;
• forming a material layer on the gate layer;
• patterning the material layer for forming sacrificial mandrels on the gate layer in the first region;
• forming sidewall spacers adjacent to the sacrificial mandrels;
• forming a dielectric layer on the sidewall spacers and the sacrificial mandrels;
• planarizing the dielectric layer, the sidewall spacers, and the sacrificial mandrels so that the top surfaces of the sidewall spacers and the sacrificial mandrels are even with the top surface of the dielectric layer;
• removing the sacrificial mandrels and the dielectric layer;
• forming a patterned mask on the second region, wherein the patterned mask is not formed by sidewall image transfer (SIT) process;
• and
• utilizing the patterned mask and the sidewall spacers to remove part of the gate layer until reaching the bottom of the gate layer.