Contact structure for FinFET semiconductor device

A semiconductor device including a FinFET, the FinFET comprising:

• a first fin structure and a second fin structure disposed over a substrate, upper portions of the first and second fin structures protruding from an isolation insulating layer;
• a gate structure over parts of the first and second fin structures;
• first epitaxial layers disposed over source/drain regions of the first and second fin structures, respectively, the first epitaxial layers being separated from each other;
• a second epitaxial layer disposed over the first epitaxial layers, the second epitaxial layer having a material composition different from the first epitaxial layer;
• a first insulating layer disposed over the second epitaxial layer,
• an interlayer dielectric (ILD) layer disposed over the first insulating;
• and
• an electrically conductive contact layer in contact with the first and second epitaxial layers,
• wherein a bottom of the electrically conductive contact layer is located closer to the substrate than an uppermost portion of the first epitaxial layer,
• an entirety of the bottom of the electrically conductive contact layer between the first fin structure and the second fin structure is in contact with the second epitaxial layer, and
• a second insulating layer is disposed between a part of the first epitaxial layer and a part of the second epitaxial layer and between the first insulating layer and the isolation insulating layer, and
• the second insulating layer is in direct contact with the part of the first epitaxial layer, the first insulating layer and the isolation insulating layer.

A semiconductor device including a FinFET, the FinFET comprising:

• three or more fin structures disposed over a substrate such that upper portions of the three or more fin structures protruding from an isolation insulating layer;
• a gate structure disposed over parts of the three or more fin structures;
• a first epitaxial layer disposed over a source/drain region of each of the three or more fin structures, the first epitaxial layer of one fin structure being separated from the first epitaxial layer of an adjacent fin structure;
• a second epitaxial layer disposed over the first epitaxial layer, the second epitaxial layer having a material composition different from the first epitaxial layer;
• a third epitaxial layer disposed over the second epitaxial layer, the third epitaxial layer having a material composition different from the second epitaxial layer;
• and
• an electrically conductive contact layer disposed in contact with the first, second and third epitaxial layers, wherein:
• the electrically conductive contact layer is in contact with an upper surface and side surfaces of an upper portion of the first epitaxial layer of each of the three or more fin structures,
• the first epitaxial layer comprises Si1-xGex, the second epitaxial layer comprises Si1-yGey, and the third epitaxial layer comprises Si1-zGez, where x<y and z<y, and
• the third epitaxial layer further comprises at least one of B and Ga in an amount of 5.0×1019 atoms/cm3 to 1.0×1021 atoms/cm3.