Semiconductor fins for FinFET devices and sidewall image transfer (SIT) processes for manufacturing the same

A method for forming a semiconductor structure comprising:

• providing a semiconductor substrate;
• forming at least one mandrel on the semiconductor substrate;
• forming a first sidewall image transfer (SIT) spacer on opposing sidewalls of the at least one mandrel;
• forming, after the forming of the at least one mandrel and the first SIT spacer, a mandrel SIT spacer on a sidewall of each of the first SIT spacers, wherein the at least one mandrel and the mandrel SIT spacer have a same width and comprise a same mandrel material as each other, and the mandrel material is selected from the group consisting of polysilicon, amorphous silicon and amorphous carbon;
• forming a second SIT spacer having a sidewall directly contacting a sidewall of each of the mandrel SIT spacers, wherein the first and second SIT spacers comprise a spacer material that differs from the mandrel material and have a same width, wherein the width of the first and second SIT spacers is less than the width of the at least one mandrel and the mandrel SIT spacer;
• removing, at the same time, the at least one mandrel and each of the mandrel SIT spacers from the sidewalls of the first and second SIT spacers, thereby defining a pattern comprising the first SIT spacers and the second SIT spacers on the semiconductor substrate;
• and
• etching the semiconductor substrate using the first SIT spacers and the second SIT spacers as an etching mask to transfer the pattern of the first SIT spacers and the second SIT spacers into the semiconductor substrate to form a plurality of semiconductor fins from the semiconductor substrate.