The device roadmap past gate-all-around (GAA) nanosheets has a leading candidate: the forksheet. Its defining feature is a dielectric wall inserted between the n-type and p-type devices, allowing them to be placed much closer together than two independent GAA stacks - shrinking the cell. Taiwan Semiconductor Manufacturing Co., Ltd. opened 2024 with a forksheet grant.
US11862700B2, "Semiconductor device structure including forksheet transistors and methods of forming the same" (issued 2024-01-02), is classified in H01L 29/42392 (gate electrodes for GAA) with H01L 21/823828 and 823857 (CMOS integration) and H01L 27/092 (complementary FET). The claim is on the forksheet structure - and the limitation that distinguishes it is the wall separating the complementary devices.
Construe the wall. In a conventional CMOS layout, n and p devices need a minimum separation set by well boundaries and isolation. The forksheet's dielectric wall lets them abut more tightly because the wall provides the isolation in a thin vertical structure. The claim turns on that separating wall and how the nanosheets sit on either side of it.
The design-around space is in the isolation scheme between n and p. A competitor achieving tight n/p spacing by another means - a different isolation structure, or the complementary-FET (CFET) approach of stacking n over p vertically - sits outside a claim that requires the specific forksheet wall. Forksheet and CFET are competing post-GAA paths, and they are claimed separately.
Filing on forksheet on the first business day of 2024 signals TSMC staking an early position on a device that is still years from volume. This is research-frontier IP, valuable as a priority-date anchor in a contest that includes imec (which originated the forksheet concept), Samsung, and Intel.
For an R&D strategist, this grant is a roadmap signal: TSMC is hedging its post-nanosheet bets, with forksheet IP alongside its GAA and packaging filings. The priority date matters because the forksheet-versus-CFET decision is one of the defining device questions of the late-2020s, and early claims will shape the freedom-to-operate landscape when it arrives.