| CPC H10B 43/27 (2023.02) [H10B 41/27 (2023.02)] | 20 Claims |

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1. A method of making a 3D multilayer semiconductor device, the method comprising:
providing a first substrate comprising a first level, said first level comprising a first single crystal silicon layer;
providing a second substrate comprising a second level, said second level comprising a second single crystal silicon layer;
performing an epitaxial growth of a SiGe layer on top of said second single crystal silicon layer;
performing an epitaxial growth of a third single crystal silicon layer on top of said SiGe layer,
wherein said third single crystal silicon layer has an average thickness of less than 2,000 nm;
forming a plurality of second transistors each comprising a single crystal channel;
forming a plurality of metal layers interconnecting said plurality of second transistors; and then
performing a bonding of said second level onto said first level,
wherein performing said bonding comprises making oxide-to-oxide bond zones; and
performing removal of a majority of said second single crystal silicon layer.
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