Source or drain structures with contact etch stop layer

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

• forming a fin comprising a semiconductor material, the fin having a lower fin portion and an upper fin portion;
• forming a gate stack over the upper fin portion of the fin, the gate stack having a first side opposite a second side;
• recessing the fin at the first side of the gate stack and at the second side of the gate stack;
• forming a first epitaxial source or drain structure on a first portion of the recessed fin at the first side of the gate stack, and forming a second epitaxial source or drain structure on a second portion of the recessed fin at the second side of the gate stack, the first and second epitaxial source or drain structures comprising a lower semiconductor layer, an intermediate semiconductor layer and an upper semiconductor layer, wherein the intermediate semiconductor layer is different in composition than the upper and lower semiconductor layers.

An integrated circuit structure, comprising:

• a fin comprising silicon;
• a gate stack over an upper fin portion of the fin, the gate stack having a first side opposite a second side;
• first and second dielectric sidewall spacers along the first and second sides of the gate stack, respectively;
• a first epitaxial source or drain structure embedded in the fin at the first side of the gate stack;
• a first conductive electrode on the first epitaxial source or drain structure;
• a first dielectric spacer along sidewalls of the first conductive electrode;
• a second epitaxial source or drain structure embedded in the fin at the second side of the gate stack;
• a second conductive electrode on the second epitaxial source or drain structure;
• and
• a second dielectric spacer along sidewalls of the second conductive electrode.