Structure and formation method of semiconductor device with low resistance contact

A method for forming a semiconductor device structure, comprising:

• forming a fin structure over a semiconductor substrate;
• forming a gate stack over the fin structure;
• forming a source/drain structure over the fin structure, wherein the source/drain structure is adjacent to the gate stack;
• applying plasma on the source/drain structure to form a modified region in the source/drain structure, wherein the modified region has lower crystallinity than an inner portion of the epitaxial structure, and the modified region extends along an exposed surface of the source/drain structure;
• forming a metal layer on the exposed surface of the source/drain structure;
• and
• heating the metal layer and the modified region to form a metal-semiconductor compound region, wherein the metal-semiconductor compound region extends along the exposed surface of the source/drain structure.

A semiconductor device structure, comprising:

• a fin structure over a semiconductor substrate;
• a gate stack over the fin structure;
• an epitaxial structure over the fin structure, wherein the epitaxial structure is adjacent to the gate stack, and the epitaxial structure has a first slanted sidewall surface facing upwards and a second slanted sidewall surface facing downwards;
• a conductive contact electrically connected to the epitaxial structure;
• and
• a metal-semiconductor compound layer extending along the first slanted sidewall surface and the second slanted sidewall surface and physically separating the conductive contact and the epitaxial structure.