Semiconductor device and method for fabricating the same

A semiconductor device, comprising:

• a substrate having a first semiconductor fin in a first region of the substrate and a second semiconductor fin in a second region of the substrate;
• a p-type FinFET in the first region, comprising:
• a first gate stack across the first semiconductor fin, comprising a first filter layer between a first work function layer and a first metal filling layer to prevent or decrease penetration of diffusion atoms in the p-type FinFET;
• and
• first strain layers beside the first gate stack;
• and
• an n-type FinFET in the second region, comprising:
• a second gate stack across the second semiconductor fin, comprising a second filter layer between a second work function layer and a second metal filling layer to prevent or decrease penetration of diffusion atoms in the n-type FinFET;
• and
• second strain layers beside the second gate stack.

A method of fabricating a FinFET, comprising:

• providing a substrate having a semiconductor fin;
• forming a gate stack across the semiconductor fin, comprising:
• forming a gate dielectric layer on the semiconductor fin;
• forming a work function layer on the gate dielectric layer;
• forming a filter layer on the work function layer to prevent or decrease penetration of diffusion atoms;
• forming a metal filling layer on the filter layer, wherein a material of the filter layer is different from a material of the metal filling layer;
• and
• forming strain layers beside the gate stack.