Fin field effect transistor (finfet) device and method for forming the same

A method for forming a fin field effect transistor (FinFET) device structure, comprising:

• providing a substrate, wherein the substrate comprises a core region and an I/O region;
• forming a fin structure above the substrate;
• forming a plurality of gate stack structures over the fin structure;
• performing a deposition process to form a film on the fin structure and the gate stack structures;
• and
• etching the film and a portion of the fin structure to form a plurality of first trenches in the core region and a plurality of second trenches in the I/O region.

A method for forming a fin field effect transistor (FinFET) device structure, comprising:

• providing a substrate, wherein the substrate comprises a core region and an I/O region;
• forming a first fin structure in the core region and a second fin structure in the I/O region;
• forming a plurality of gate stack structures over the first fin structure and the second fin structure, wherein a pattern density of the gate stack structures in the core region is greater than a pattern density of the gate stack structures in the I/O region;
• performing a deposition process to form a film on the first fin structure, the second fin structure and the gate stack structures;
• and
• etching the film and a portion of the first fin structure and a portion of the second fin structure to form a plurality of first trenches in the core region and a plurality of second trenches in the I/O region.

A method for forming a fin field effect transistor (FinFET) device structure, comprising:

• providing a substrate, wherein the substrate comprises a core region and an I/O region;
• forming a first fin structure in the core region and a second fin structure in the I/O region;
• forming a plurality of gate stack structures over the first fin structure and the second fin structure;
• performing a deposition process to form a film on the first fin structure, the second fin structure and the gate stack structures, wherein a thickness of the film in the core region is smaller than a thickness of the film in the I/O region;
• and
• etching the film and a portion of the first fin structure and a portion of the second fin structure to form a first etched fin structure directly below the gate stack structure in the core region and a second etched fin structure directly below the gate stack structure in the I/O region, wherein the gate stack structures have a first width, a width of the first etched fin structure is smaller than the first width, and a width of the second etched fin structure is greater than the first width.