Patent attributes
A semiconductor device includes semiconductor nanostructures disposed over a substrate, a source/drain epitaxial layer in contact with the semiconductor nanostructures, a gate dielectric layer disposed on and wrapping around each channel region of the semiconductor nanostructures, a gate electrode layer disposed on the gate dielectric layer and wrapping around each channel region, and insulating spacers disposed in spaces, respectively. The spaces are defined by adjacent semiconductor nanostructures, the gate electrode layer and the source/drain region. The source/drain epitaxial layer includes multiple doped SiGe layers having different Ge contents and at least one of the source/drain epitaxial layers is non-doped SiGe or Si.