Semiconductor device having a cap layer with V-shape
A method for fabricating semiconductor device is disclosed. First, a substrate is provided, and a gate structure is formed on the substrate. Next, a recess is formed adjacent to two sides of the gate structure, and an epitaxial layer is formed in the recess, in which a top surface of the epitaxial layer is lower than a top surface of the substrate. Next, a cap layer is formed on the epitaxial layer, in which a top surface of the cap layer is higher than a top surface of the substrate.
1. A semiconductor device, comprising:
a substrate;
a gate structure on the substrate;
an epitaxial layer structure in the substrate adjacent to two sides of the gate structure; and
a cap layer on the epitaxial layer, wherein the cap layer comprises a first V-shape and a first valley point of the first V-shape is lower than a top surface of the substrate.
2. The semiconductor device of claim 1 , further comprising a buffer layer between the epitaxial layer and the substrate.
3. The semiconductor device of claim 2 , wherein the buffer layer comprises silicon phosphide (SiP).
4. The semiconductor device of claim 1 , wherein the epitaxial layer and the cap layer comprises SiP.
5. The semiconductor device of claim 4 , wherein a concentration of the phosphorus in the cap layer is lower than a concentration of the phosphorus in the epitaxial layer.
6. The semiconductor device of claim 1 , wherein a top surface of the epitaxial layer comprises a second V-shape and a second valley point of the second V-shape is lower than a top surface of the substrate.
7. The semiconductor device of claim 1 , further comprising a contact plug contacting the cap layer.
8. The semiconductor device of claim 1 , wherein a thickness of the cap layer is between 10-100 Angstroms.