Strained CMOS on strain relaxation buffer substrate

1. A FinFET device comprising:

a strain relaxation buffer (SRB) substrate;

a set of cut silicon fins on the SRB substrate, each fin in the set of cut silicon fins having a pair of long vertical faces and a pair of short vertical faces, where pairs of the cut silicon fins are oriented so that respective short vertical faces of the pair are oriented opposite to each other;

a set of cut silicon germanium fins on the SRB substrate, each fin in the set of silicon germanium fins having a pair of long vertical faces and a pair of short vertical faces, where pairs of the cut silicon germanium fins are oriented so that respective short vertical faces of the pair are oriented opposite to each other;

a set of tensile dielectric structures, wherein respective ones of the tensile dielectric structures bridge between the short vertical faces of respective pairs of the cut silicon fins to maintain tensile strain at the fin ends of the pair of cut silicon fins; and

a set of compressive dielectric structures, wherein respective ones of the compressive dielectric structure bridge between the short vertical faces of respective pairs of the cut silicon germanium fins to maintain compressive strain at the fin ends of the pair of cut silicon germanium fins.

2. The device as recited in claim 1 , wherein the set of silicon fins is comprised of an epitaxial silicon layer which is tensily strained for a set of n-type FinFET devices, and wherein the set of silicon germanium fins is comprised of an epitaxial silicon germanium layer which is compressively strained for a set of p-type FinFET devices.

3. The device as recited in claim 1 , wherein respective ones of the set of the tensile dielectric structures bridge between the short vertical faces of at least two pairs cut silicon fins and wherein respective ones of the set of compressive dielectric structures bridge between the short vertical faces of at least two pairs of two cut silicon germanium fins.

4. The device as recited in claim 2 , wherein a thickness of the tensile dielectric structures is greater than a thickness of silicon channels in the set of silicon fins and a thickness of the compressive dielectric structures is greater than a thickness of silicon germanium channels in the silicon germanium fins.

5. The device as recited in claim 2 , wherein the tensile dielectric structures are comprised of a tensile silicon nitride.

6. The device as recited in claim 2 , wherein the compressive dielectric structures are comprised of a compressive silicon nitride.

7. The device as recited in claim 4 , wherein a bottom surface of the tensile dielectric structures is below a bottom surface of the silicon channels in the set of silicon fins.

8. The device as recited in claim 2 , wherein the strain relaxation buffer (SRB) substrate comprises a SiGe layer with a lower atomic percentage of germanium than the epitaxial silicon germanium layer.

9. The device as recited in claim 1 , wherein a respective one of the set of the tensile dielectric structures bridges between the vertical face of a fin end of a cut silicon fin and a first dummy feature and wherein a respective one of the set of compressive dielectric structures bridges between the vertical face of a fin ends of a cut silicon germanium fin and a second dummy feature.