Structures and formation methods of a semiconductor device structure are provided. The method includes forming a fin structure over a semiconductor substrate and forming a gate stack over the fin structure. The method also includes forming an epitaxial structure over the fin structure. The method further includes forming a dielectric layer over the epitaxial structure and forming an opening in the dielectric layer to expose the epitaxial structure. In addition, the method includes forming a modified region in the epitaxial structure. The modified region has lower crystallinity than an inner portion of the epitaxial structure and extends along an entirety of an exposed surface of the epitaxial structure. The method also includes forming a semiconductor-metal compound region on the epitaxial structure. All or some of the modified region is transformed into the semiconductor-metal compound region.