Gate-all-around integrated circuit structures having self-aligned source or drain undercut for varied widths

A method of fabricating an integrated circuit structure, the method comprising:

• forming a first vertical arrangement of nanowires and a second vertical arrangement of nanowires above a substrate, the nanowires of the second vertical arrangement of nanowires having a horizontal width greater than a horizontal width of the nanowires of the first vertical arrangement of nanowires;
• forming a first gate stack portion over the first vertical arrangement of nanowires and a second gate stack portion over the second vertical arrangement of nanowires;
• forming first dielectric sidewall spacers along the first and second gate stack portions;
• implanting impurity atoms into portions of the first vertical arrangement of nanowires and the second vertical arrangement of nanowires that are not covered by the first dielectric sidewall spacers;
• forming second dielectric sidewall spacers along the first and second gate stack portions;
• removing the portions of the first vertical arrangement of nanowires and the second vertical arrangement of nanowires implanted with the impurity atoms to form recessed ends of the first and second vertical arrangements of nanowires;
• forming first embedded epitaxial source or drain regions at the recessed ends of the first vertical arrangement of nanowires, the first embedded epitaxial source or drain regions extending beneath the second dielectric sidewalls spacers by a first distance;
• and
• forming second embedded epitaxial source or drain regions at the recessed ends of the second vertical arrangement of nanowires, the second embedded epitaxial source or drain regions extending beneath the second dielectric sidewalls spacers by a second distance substantially the same as the first distance.

An integrated circuit structure, comprising:

• a first fin having a longest dimension along a first direction;
• a first nanowire over the first fin;
• a second fin having a longest dimension along the first direction;
• a second nanowire over the second fin, wherein the second nanowire is wider than the nanowire;
• a first gate structure over the first nanowire and the first fin, the first gate structure having a longest dimension along a second direction, the second direction orthogonal to the first direction;
• a second gate structure over the second nanowire and over the second fin, the second gate structure having a longest dimension along the second direction, the second gate structure discontinuous with the first gate structure along the second direction, and the second gate structure having an edge facing an edge of the first gate structure along the second direction;
• a gate endcap isolation structure between and in contact with the edge of the first gate structure and the edge of the second gate structure along the second direction, the gate endcap isolation structure having a length along the first direction greater than a length of the first gate structure and the second gate structure along the first direction;
• first dielectric sidewall spacers along the first gate structure;
• second dielectric sidewall spacers along the second gate structure;
• first embedded epitaxial source or drain regions at ends of the first nanowire, the first embedded epitaxial source or drain regions extending beneath the first dielectric sidewalls spacers by a first distance;
• and
• second embedded epitaxial source or drain regions at ends of the second nanowire, the second embedded epitaxial source or drain regions extending beneath the second dielectric sidewalls spacers by a second distance substantially the same as the first distance.