Sub-lithographic semiconductor structures with non-constant pitch

1. A method of forming a plurality of fins, comprising:

forming a first set of fins having a first pitch;

forming an adjacent fin to the first set of fins,

forming an intermediate island between the adjacent fin and a nearest fin of the first set of fins, and

removing the intermediate island so that the adjacent fin is spaced apart from the nearest fin of the first set of fins by a second pitch larger than the first pitch,

wherein the first set of fins, the intermediate island, and the adjacent fin are sub-lithographic features formed using a sidewall image transfer process.

2. The method of claim 1 , wherein:

the first set of fins initially comprise:

a first structure of a first group of materials; and

a second structure of a second group of materials; and

the adjacent fin initially comprises a third structure comprising the second group of materials,

wherein an underlying material of the first group of materials and an underlying material of the second group of materials is a same material which form a first fin and a second fin of the first set of fins, and the adjacent fin.

3. The method of claim 2 , further comprising:

removing material from over the underlying material from the second structure and the third structure through same processing steps to form the second fin and the adjacent fin; and

removing material from over the underlying material from the first structure to form the first fin.

4. The method of claim 3 , wherein the removing the material from the first structure is performed in different processing steps than removing the material from the second structure and the third structure.

5. The method of claim 3 , wherein:

the removing the material from the first structure comprises removing a hard mask, and the underlying material is silicon; and

the removing the material from the second structure and the third structure comprises removing a spacer material and an etch stop material, and the underlying material is silicon.

6. The method of claim 2 , further comprising forming another fin adjacent to the adjacent fin and remote from the first set of fins, the another fin and the adjacent fin have a pitch of equal or substantially equal size to the second pitch.

7. The method of claim 6 , further comprising forming an additional fin adjacent to the another fin and remote from the first set of fins, the additional fin and the adjacent fin have a pitch is equal or substantially equal to the second pitch.

8. The method of claim 7 , further comprising forming a second set of fins, adjacent to the additional fin, wherein:

the second set of fins has a pitch that is equal or substantially equal to the first pitch; and

the additional fin and a nearest fin of the second set of fins has a pitch that is equal or substantially equal to the second pitch.

9. The method of claim 1 , wherein:

the first set of fins comprise:

a first fin initially comprising an etch stop material formed on a substrate, and a sidewall spacer material formed on the etch stop material; and

a second fin initially comprising a masking material formed on the substrate material; and the adjacent fin initially comprises the etch stop material formed on the substrate, and the sidewall spacer material formed on the etch stop material;

the etch stop layer and the sidewall spacer are removed during a selective etching process to form the first fin and the adjacent fin; and

the masking material is removed in a separate etching process to form the second fin.

10. The method of claim 9 , wherein the first fin and the adjacent fin are formed in same processing steps.

11. The method of claim 9 , wherein the sidewall spacer material is formed during the sidewall image transfer process.

12. The method of claim 1 , further comprising forming another fin adjacent to the adjacent fin and remote from the first set of fins, the another fin and the adjacent fin have a pitch of equal or substantially equal size to the second pitch.