Semiconductor device and method for fabricating the same

1. A method for fabricating semiconductor device, comprising:

providing a substrate having a first region, a second region, and a third region;

forming mandrels on the first region, the second region, and the third region;

forming spacers adjacent to the mandrels;

removing the mandrels;

forming a first patterned mask to cover the spacers on the first region and the second region after removing the mandrels; and

removing the spacers on the third region.

2. The method of claim 1 , further comprising:

forming a pad oxide on the substrate;

forming a pad nitride on the pad oxide;

forming the mandrels on the pad nitride;

forming a cap layer on the mandrels;

removing part of the cap layer; and

removing the mandrels for forming the spacers on the first region, the second region, and the third region.

3. The method of claim 1 , further comprising:

removing the first patterned mask;

forming a second patterned mask on the third region;

removing part of the substrate to form first fin-shaped structures on the first region and second fin-shaped structures on the second region;

forming a third patterned mask on part of the first fin-shaped structures and part of the second fin-shaped structures;

removing part of the first fin-shaped structures and part of the second fin-shaped structures; and

removing part of the substrate to form a first base under the first fin-shaped structures, a second base under the second fin-shaped structures, and a first trench between the first base and the second base.

4. The method of claim 3 , further comprising:

removing the second patterned mask and the third patterned mask;

forming a fourth patterned mask on the third region, the first region, and the second fin-shaped structures; and

removing part of the second base on the second region to form a second trench between the second fin-shaped structures.

5. The method of claim 4 , wherein the depths of the first trench and the second trench are different.

6. The method of claim 1 , further comprising:

removing the first patterned mask;

forming a second patterned mask on the first region and the third region;

removing part of the substrate on the second region;

removing the second patterned mask;

forming a third patterned mask on the third region;

removing part of the substrate on the first region and the second region to form first fin-shaped structures and second fin-shaped structures;

forming a fourth patterned mask on the first region and the second region;

removing part of the first fin-shaped structures and part of the second fin-shaped structures; and

removing part of the substrate to form a base under the first fin-shaped structures and a trench between the first fin-shaped structures and the second fin-shaped structures.

7. The method of claim 6 , wherein the bottom of the trench and the bottom of the second fin-shaped structures are coplanar.

8. The method of claim 1 , further comprising:

removing the first patterned mask;

forming a second patterned mask on the third region;

removing part of the substrate to form first fin-shaped structures on the first region and the second region;

forming a third patterned mask on the first fin-shaped structures of the first region;

removing part of the substrate on the second region to form second fin-shaped structures;

removing the third patterned mask;

forming a fourth patterned mask on the first region and the second region;

removing part of the first fin-shaped structures and part of the second fin-shaped structures; and

removing part of the substrate to form a base under the first fin-shaped structures and a trench between the first fin-shaped structures and the second fin-shaped structures.

9. The method of claim 8 , wherein the bottom of the trench and the bottom of the second fin-shaped structures are coplanar.