Semiconductor device and method for fabricating the same
A semiconductor device including a first fin protruding on a substrate and extending in a first direction; a first gate electrode on the first fin, the first gate electrode intersecting the first fin; a first trench formed within the first fin at a side of the first gate electrode; a first epitaxial layer filling a portion of the first trench, wherein a thickness of the first epitaxial layer becomes thinner closer to a sidewall of the first trench; and a second epitaxial layer filling the first trench on the first epitaxial layer, wherein a boron concentration of the second epitaxial layer is greater than a boron concentration of the first epitaxial layer.
1. A semiconductor device, comprising:
a first fin protruding on a substrate and extending in a first direction;
a first gate electrode on the first fin, the first gate electrode intersecting the first fin;
a first trench formed within the first fin at a side of the first gate electrode;
a first epitaxial layer filling a portion of the first trench, wherein a thickness of the first epitaxial layer becomes thinner closer to a sidewall of the first trench; and
a second epitaxial layer filling the first trench on the first epitaxial layer,
wherein a boron concentration of the second epitaxial layer is greater than a boron concentration of the first epitaxial layer.
2. The semiconductor device as claimed in claim 1 , wherein:
the first fin includes silicon, and
the first epitaxial layer and the second epitaxial layer each include silicon germanium.
3. The semiconductor device as claimed in claim 2 , wherein a germanium concentration of the first epitaxial layer is lower than a germanium concentration of the second epitaxial layer.
4. The semiconductor device as claimed in claim 1 , wherein the first epitaxial layer includes:
a first portion on a bottom surface of the first trench; and
a second portion on a side surface of the first trench.
5. The semiconductor device as claimed in claim 4 , wherein a thickness of the first portion is thicker than a thickness of the second portion.
6. The semiconductor device as claimed in claim 4 , wherein the second portion is in contact with the first gate electrode.
7. The semiconductor device as claimed in claim 1 , further comprising a third epitaxial layer between the second epitaxial layer and the first epitaxial layer, wherein a germanium concentration of the third epitaxial layer is lower than a germanium concentration of the second epitaxial layer.
8. The semiconductor device as claimed in claim 7 , wherein a germanium concentration of the third epitaxial layer is higher than a germanium concentration of the first epitaxial layer.
9. The semiconductor device as claimed in claim 1 , wherein an upper surface of the first epitaxial layer has a U shape in cross section.
10. The semiconductor device as claimed in claim 1 , further comprising a first gate spacer on a sidewall of the first gate electrode, wherein the first trench is in contact with a lower surface of the first gate spacer.