replacement metal gate

**RMG** (Replacement Metal Gate) is the **gate-last integration scheme where a sacrificial polysilicon dummy gate is replaced with the final high-k dielectric and metal gate stack after all high-temperature processing is complete** — the industry-standard approach for all advanced CMOS nodes. **RMG Process Flow** - **Dummy Gate**: Deposit and pattern sacrificial poly-Si gate on thin oxide. - **S/D Formation**: Form spacers, implant/epitaxially grow source/drain, high-temperature activation anneal. - **ILD + CMP**: Deposit interlayer dielectric and planarize to expose the dummy gate top. - **Gate Removal**: Selectively etch out the dummy poly-Si (and thin oxide). - **HKMG Deposition**: Deposit interfacial layer, high-k, work function metals, and fill metal into the gate trench. - **CMP**: Planarize excess metal to complete the gate. **Why It Matters** - **V$_t$ Control**: Metal gate is never exposed to high temperatures — enables precise work function tuning. - **Multi-V$_t$**: Different work function metals for different V$_t$ flavors (LP, SP, HP, uLP) using selective metal deposition. - **Standard**: Used by Intel (from 45nm), TSMC, Samsung from 28/20nm through all current nodes. **RMG** is **building the gate last** — replacing a sacrificial placeholder with the real metal gate after all hot steps are done.