Method of manufacturing a semiconductor device and a semiconductor device

A method of manufacturing a semiconductor device including a fin field effect transistor (Fin FET), the method comprising:

• forming a plurality of fin structures over a substrate, the plurality of fin structures extending in a first direction and arranged in a second direction crossing the first direction;
• forming an isolation insulating layer over the substrate so that lower portions of the plurality of fin structures are embedded in the isolation insulating layer and upper portions of the plurality of fin structures are exposed from the isolation insulating layer;
• recessing the source/drain regions of the plurality of fin structures to form recesses;
• and
• forming an epitaxial source/drain structure over each of the recess of the fin structures to form a merged source/drain epitaxial layer,
• wherein in the recessing the source/drain regions, a plasma etching process combining etching and deposition processes is used, and
• a bottom of each of the recesses has a W-shape or a wavy shape.

A semiconductor device comprising:

• an isolation insulating layer disposed over a substrate,
• a fin structure disposed over the substrate and extending in a first direction in plan view,
• a gate structure disposed over a part of the fin structure,
• a source/drain epitaxial layer over a source/drain region of the fin structure;
• and
• a dielectric layer disposed on a upper surface of the isolation insulating layer, wherein,
• an interface between the source/drain epitaxial layer and the source/drain region of the fin structure has a W-shape.