Semiconductor device and method for fabricating the same

A method for fabricating semiconductor device, comprising:

• providing a substrate having a first region and a second region;
• forming a first fin-shaped structure on the first region and a second fin-shaped structure on the second region, wherein each of the first fin-shaped structure and the second fin-shaped structure comprises a top portion and a bottom portion;
• forming a shallow trench isolation (STI) around the bottom portions of the first fin-shaped structure and the second fin-shaped structure;
• forming a patterned mask on the second region after forming a first gate structure on the first fin-shaped structure and a second gate structure on the second fin-shaped structure;
• performing a process to enlarge the first fin-shaped structure so that the top surfaces of the first fin-shaped structure and the second fin-shaped structure are different, wherein the process comprises performing an epitaxial growth process to form a semiconductor layer on the first fin-shaped structure;
• and
• transforming the first gate structure and the second gate structure into a first metal gate and a second metal gate.