Patent ID: 8841197

Claim:
A method for forming a fin structure, comprising the following steps: forming a multiple layer structure on a substrate; forming a sacrificial pattern on the multiple-layer structure; forming a spacer on the sidewall of the sacrificial pattern that is disposed on the multiple-layer structure; removing the sacrificial pattern; using the spacer as a cap layer to etch parts of the multiple-layer structure, and then using the multiple-layer structure as a cap layer to etch the substrate to form at least one fin structure and at least one first shallow trench in the substrate; filling a first insulation layer in each first shallow trench; performing a planarization process to the first insulation layer; then forming at least one second shallow trench in the substrate, wherein the second shallow trench is deeper than the first shallow trench; filling a second insulation layer in each second shallow trench; and performing another planarization process to the second insulation layer.