US Patent 9418994 Fin field effect transistor (FinFET) device structure

A fin field device structure and method for forming the same are provided. The FinFET device structure includes a substrate, and the substrate includes a first region and a second region. The FinFET device structure includes an isolation structure formed on the substrate and first fin structures formed on the first region. The FinFET device structure also includes second fin structures formed on the second region, and the number of the first fin structures is greater than the number of the second fin structures. The first fin structures have a first height, the second fin structures have a second height, and a gap between the first height and the second height is in a range from about 0.4 nm to about 4 nm.