Method and structure for srb elastic relaxation

A device comprising:

• a silicon germanium (SiGe) strained relaxed buffer (SRB) on a silicon (Si) substrate;
• a Si layer over the SiGe SRB;
• an n-type field-effect transistor (NFET) channel and a SiGe p-type FET (PFET) channel in the Si layer and adjacent to each other;
• a silicon nitride (SiN) layer over the NFET and PFET channels;
• first and second cuts formed through the SiN layer, the NFET and PFET channels, respectively, and the SiGe SRB down to the Si substrate, the first and second cuts on opposite ends of the Si substrate and perpendicular to the NFET and PFET channels;
• fins in the SiGe SRB through the SiN layer and the NFET and PFET channels, the fins formed perpendicular to the first and second cuts;
• a first oxide layer between the fins;
• a third cut formed between the NFET and PFET channels down into the SiGe SRB, the third cut being parallel to the fins;
• and
• a second oxide layer filling the third cut,
• wherein the first and second oxide layers are recessed down to the SiGe SRB.

A device comprising:

• a silicon germanium (SiGe) strained relaxed buffer (SRB) on a silicon (Si) substrate;
• a first silicon nitride (SiN) layer over the SiGe SRB;
• first and second cuts through the SiN layer and SiGe SRB, the first and second cuts formed on opposite ends of the Si substrate;
• a first oxide layer within the first and second cuts;
• a Si layer on the SiGe SRB;
• an n-type field-effect transistor (NFET) channel and a SiGe p-type FET (PFET) channel in the Si layer and adjacent to each other;
• a second SiN layer over the NFET and PFET channels and first oxide layer;
• fins in the SiGe SRB through the second SiN layer and the NFET and PFET channels, the fins formed perpendicular to the first and second cuts;
• a second oxide layer between the fins;
• a third cut between the NFET and PFET channels down into the SiGe SRB, the third cut formed parallel to the fins;
• and
• a second oxide within the third cut, wherein the second and third oxide layers are recessed down to the SiGe SRB.