Semiconductor device and method for fabricating the same
A method for fabricating semiconductor device includes the steps of first forming a metal gate on a substrate and a spacer around the metal gate, in which the metal gate comprises a high-k dielectric layer, a work function metal layer, and a low-resistance metal layer. Next, part of the high-k dielectric layer is removed to form an air gap between the work function metal layer and the spacer.
1. A semiconductor device, comprising:
a metal gate on a substrate, wherein the metal gate comprises:
a high-k dielectric layer;
a work function metal layer on the high-k dielectric layer; and
a metal layer on the work function metal layer;
a spacer around the metal gate; and
an air gap between the work function metal layer and the spacer and contacts the high-k dielectric layer directly.
2. The semiconductor device of claim 1 , wherein the high-k dielectric layer and the work function metal layer are U-shaped.
3. The semiconductor device of claim 1 , wherein a top surface of the metal layer is higher than a top surface of the work function metal layer.
4. The semiconductor device of claim 1 , wherein a top surface of the work function metal layer is higher than a top surface of the high-k dielectric layer.
5. The semiconductor device of claim 1 , further comprising a hard mask on the work function metal layer and the metal layer.
6. The semiconductor device of claim 5 , wherein the air gap is between the hard mask and the high-k dielectric layer.
7. The semiconductor device of claim 5 , further comprising an interlayer dielectric (ILD) layer around the spacer.
8. The semiconductor device of claim 7 , wherein the top surfaces of the hard mask and the ILD layer are coplanar.