Method for source/drain contact formation in semiconductor devices

A semiconductor device, comprising:

• first and second gate stacks;
• first and second gate spacers over sidewalls of the first and second gate stacks respectively;
• first and second source/drains adjacent the first and second gate stacks respectively and comprising different semiconductor materials;
• first and second contacts disposed over the first and second source/drains respectively, wherein a bottom surface of the first contact is lower than a bottom surface of the second contact;
• a contact etch stop layer over sidewalls of the first and second gate spacers and over the first and second source/drains;
• and
• a protective dielectric layer between the contact etch stop layer and the first and second contacts.

A semiconductor device, comprising:

• a first region including:
• a first n-type semiconductor layer in a source/drain (S/D) region of the first region;
• a second n-type semiconductor layer in another S/D region of the first region;
• and
• a first gate stack between and adjacent to both the first and the second n-type semiconductor layers;
• a second region including:
• a first p-type semiconductor layer in an S/D region of the second region;
• a second p-type semiconductor layer in another S/D region of the second region;
• and
• a second gate stack between and adjacent to both the first and the second p-type semiconductor layers,
• wherein a lowest point of an upper surface of the first n-type semiconductor layer is below a lowest point of an upper surface of the second n-type semiconductor layer, and a lowest point of an upper surface of the first p-type semiconductor layer is below a lowest point of an upper surface of the second p-type semiconductor layer.