Method of fabricating stacked semiconductor device

A method of forming a semiconductor device, the method comprising:

• forming a fin cut mask over a semiconductor fin structure extending horizontally over a substrate, the semiconductor fin structure comprising lower and upper channel layers separated by an intermediate layer, wherein the fin cut mask covers the semiconductor fin structure in a channel region and exposes the semiconductor fin structure in fin cut regions on opposite sides of the channel region;
• forming preliminary fin cuts in the semiconductor fin structure by partially etching through the semiconductor fin structure in the fin cut regions, wherein partially etching extends the preliminary fin cuts through the upper channel layer in the fin cut regions to define an upper channel layer portion in the channel region;
• forming a sacrificial spacer covering end surfaces of the upper channel layer portion which are exposed in the fin cut regions on opposing sides of the channel region;
• forming final fin cuts in the semiconductor fin structure by further etching through the semiconductor fin structure in the fin cut regions, wherein further etching extends the final fin cuts into the lower channel layer in the fin cut regions to define a lower channel layer portion in the channel region;
• forming epitaxial lower source/drain regions on end surfaces of the lower channel layer portion which are exposed in the fin cut regions on the opposing sides of the channel region;
• removing the sacrificial spacer, thereby exposing the end surfaces of the upper channel layer portion;
• and
• forming epitaxial upper source/drain regions on the end surfaces of the upper channel layer portion.