Gate-all-around (GAA) nanosheet
Beginner
A transistor whose channel is a few thin ribbons stacked on top of each other, each completely surrounded by the gate.
Novice
The successor to the FinFET. The channel is a stack of thin horizontal silicon sheets, and the gate wraps all the way around each one. That gives even better control, and the sheets can be made wider or narrower to tune the current. Companies call it MBCFET or RibbonFET.
Expert
Stacked nanosheets (typically three) released from a Si/SiGe superlattice by selectively etching the SiGe, then wrapped with a high-k/metal gate by atomic layer deposition. Sheet thickness, not fin width, sets , and the sub-channel leakage path of the fin disappears. Width is continuous within a cell but limited by n-p spacing and sheet stack height.
Explained in Shrinking (Transistors).
See also: FinFET, Forksheet, CFET (complementary FET).