Semiconductor structures and fabrication methods are provided. An exemplary fabrication method includes providing a substrate having a first region, second regions and third regions; and forming a patterned structure on the substrate. The patterned structure includes at least one first patterned layer on the first region, at least one second patterned layer on the second region and at least one third patterned layer on the third region, the at least one first patterned layer is discrete from the at least one second region and the at least one second region is discrete from the at least one third region. The method also includes removing the second patterned layer; and etching the substrate using the first patterned layer and the third patterned layer as an etching mask to form a base substrate, the first fin on the base substrate and the third fin on the base substrate.