Semiconductor device and method for fabricating the same
A semiconductor device includes: a substrate, a gate structure on the substrate, and a spacer adjacent to the gate structure, in which the spacer extends to a top surface of the gate structure, a top surface of the spacer includes a planar surface, the spacer encloses an air gap, and the spacer is composed of a single material. The gate structure includes a high-k dielectric layer, a work function metal layer, and a low resistance metal layer, in which the high-k dielectric layer is U-shaped. The semiconductor device also includes an interlayer dielectric (ILD) layer around the gate structure and a hard mask on the spacer, in which the top surface of the hard mask is even with the top surface of the ILD layer.
1. A semiconductor device, comprising:
a substrate;
a gate structure on the substrate and an interlayer dielectric (ILD) layer around the gate structure; and
a spacer enclosing an air gap adjacent to the gate structure and extending to and contacting a top surface of the gate structure, wherein the spacer is composed of a single material and a top surface of the spacer directly on top of the gate structure is lower than a top surface of the ILD layer.
2. The semiconductor device of claim 1 , wherein the gate structure comprises a high-k dielectric layer, a work function metal layer, and a low resistance metal layer.
3. The semiconductor device of claim 2 , wherein the high-k dielectric layer is U-shaped.
4. The semiconductor device of claim 1 , wherein a top surface of the spacer comprises a planar surface.
5. The semiconductor device of claim 1 , further comprising a hard mask on the spacer, wherein a top surface of the hard mask and a top surface of the ILD layer are coplanar.
6. The semiconductor device of claim 5 , wherein the hard mask comprises silicon nitride.
7. The semiconductor device of claim 1 , wherein the spacer comprises silicon dioxide.