The present disclosure provides a semiconductor structure and a method for forming a semiconductor structure. The method for forming a semiconductor structure includes forming a semiconductor stack over a substrate, wherein the semiconductor stack includes a plurality of first semiconductor layers and a plurality of second semiconductor layers alternatively stacked, patterning the semiconductor stack to form a first fin and a second fin adjacent to the first fin, and removing the second semiconductor layers to obtain a first group of nanosheets over the first fin and a second group of nanosheets over the second fin, wherein a lateral spacing between one of the nanosheets in the first group and a corresponding nanosheet in the second group is smaller than a vertical spacing between each of the nanosheets in the first group.