Structure and formation method of finfet device

A semiconductor device structure, comprising:

• a semiconductor substrate;
• a germanium-containing fin structure over the semiconductor substrate;
• a metal gate stack over a portion of the germanium-containing fin structure;
• and
• a semiconductor blocking layer between the germanium-containing fin structure and the metal gate stack.

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 contact layer over a portion of the fin structure, wherein the contact layer comprises a metal material, and the contact layer extends along the gate stack without protruding from a top surface of the gate stack;
• and
• driving a portion of the metal material from the contact layer into the fin structure.