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The GAAfet, aka the surrounding gate transistor (SGT), is basically a FinFET that surrounds the channel on all 4 sides instead of 3. However, a lot of examples show a cylinder instead of a rectangle.

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(source website)

I've been searching for info about them for days, but cannot find any overview of the manufacturing process. The only ones I can find that are being built in bulk appear to be rectangular. Example Samsung's MBCFET.

So basically my question is, how are cylindrical GAAfets manufactured? Is there a lithography and etching process? If so I don't understand how it reaches all around the cylinder. Light can only come from one direction at a time, and you need to be able to build/etch the entire wafer at once.

Note: I'm not asking for a full course on device physics and semiconductor fabs. I have spent some time reading about them, and I can find tons of info about traditional manufacturing process. But I cannot find anything, or hardly anything, about manufacture process for cylindrical GAAfet.

One more thing. I have heard of silicon nanowires. My understanding is that they're manufactured in bulk as discreet objects. To then take those and mechanically place them onto a wafer seems...infeasible. It would take an eternity to set and "solder" 10 billion of them.

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    \$\begingroup\$ Wire GAAFETs are essentially just narrower versions of rectangular GAAFETs. As the rectangular sheet gets narrower it becomes more cylindrical and less rectangular. Both are fabricated by epitaxial growth of the layered stack and then etching away layers and replacing them with dielectric and metal to form the gate. \$\endgroup\$
    – user1850479
    Commented Oct 25, 2021 at 3:17
  • \$\begingroup\$ @user1850479 Can you link to a site or pdf that goes into details or at least an outline? I'm really hunting for this and found zero so far. \$\endgroup\$
    – DrZ214
    Commented Oct 25, 2021 at 5:21
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    \$\begingroup\$ Since this is an active area of research, details would be in various research papers and conference presentations, so check Google scholar for how the etch is done. I see a few brief summaries on Google, although they add little more than my one sentence summary. For example: semiengineering.com/moving-to-gaa-fets \$\endgroup\$
    – user1850479
    Commented Oct 25, 2021 at 16:18

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