FinFET device on silicon-on-insulator and method of forming the same

A method of forming a fin field effect transistor on a silicon-on-insulator substrate, comprising:

• providing a substrate having a first area and a second area, wherein said substrate comprises a silicon-on-insulator substrate with a dielectric layer;
• forming a stack structure on said dielectric layer, wherein said stack structure comprises a first single crystal layer and a second single crystal layer sequentially stacked on said dielectric layer;
• forming a plurality of fin structures in said first area and said second area wherein said fin structures are disposed on said dielectric layer of said silicon-on-insulator substrate and comprise said first single crystal layer and said second single crystal layer;
• forming an insulating layer covering said fin structures in said first area and said second area;
• partially removing said insulating layer in said first area and forming a plurality of first fin structure with a first height;
• partially removing said fin structures and said insulating layer in said second area and forming a plurality of second fin structures with a second height, wherein said first height and said second height are different, and the top surface of said first fin structure and the top surface of said second fin structure are at different levels.