Semiconductor device and manufacturing methods thereof

A method, comprising:

• forming, in a device region of a semiconductor wafer, a plurality of fin structures in a substrate of the semiconductor wafer;
• forming a merged epitaxial region on a first concave recess, in a first fin structure of the plurality of fin structures, and a second concave recess, in a second fin structure of the plurality of fin structures,
• wherein a depth of the first concave recess in the first fin structure is different from a depth of the second concave recess in the second fin structure, and
• wherein the merged epitaxial region comprises a first epitaxial region and a second epitaxial region that are connected in at least a portion of the first epitaxial region and in at least a portion of the second epitaxial region;
• and
• forming a third epitaxial region on a third fin structure of the plurality of fin structures,
• wherein a height of a top surface of the first epitaxial region or the second epitaxial region is different than a height of a top surface of the third epitaxial region.

A method, comprising:

• forming, in a device region of a semiconductor wafer, a plurality of fin structures in a substrate of the semiconductor wafer;
• forming a plurality of sidewall spacers on the plurality of fin structures,
• wherein the plurality of sidewall spacers comprises a first sidewall spacer and a second sidewall spacer that are on opposing sides of a first fin structure or a second fin structure and that have different heights;
• and
• forming a merged epitaxial region on a first concave recess, in the first fin structure, and on a second concave recess, in the second fin structure,
• wherein a depth of the first concave recess in the first fin structure is different from a depth of the second concave recess in the second fin structure, and
• wherein the merged epitaxial region comprises a first epitaxial region and a second epitaxial region that are connected in at least a portion of the first epitaxial region and in at least a portion of the second epitaxial region.