Silicon Capacitor Primer
[Full primer content as delivered in chat above — written to vault for reference and cross-linking]
What they are
A silicon capacitor is a chip-form capacitor fabricated on a silicon wafer using semiconductor lithography and etching. Trenches are etched into silicon to maximize surface area, coated with high-permittivity dielectric (Al2O3 or HfO2 via atomic layer deposition), then metallized. Result is a passive that looks and behaves more like a tiny silicon die than a traditional ceramic capacitor.
How they differ from MLCC
Silicon capacitors win on ultra-thin form factor (80-100 micrometers vs 200-1,000 for MLCC), ultra-low ESL (<0.1 nH vs 0.3-1 nH), and effective frequency response above 1 GHz (vs ~100 MHz for MLCC). They lose on cost ($0.10-1 each vs $0.001-0.10 for MLCC) and maximum capacitance (mostly <100 nF vs up to 220 µF in 1206-size MLCC).
They do not replace MLCC in volume applications. They complement MLCC in three specific places: ultra-high frequency, ultra-thin packaging, and embedded-in-substrate.
Why they're the new bottleneck
AI accelerator packaging is moving to 2.5D technologies (Intel EMIB, TSMC CoWoS-S, Samsung I-Cube) that integrate multiple silicon dies onto a common substrate. Each die needs power delivery integrated as close to the silicon as the package allows. MLCC on the PCB is too far; even MLCC on the package top is too far for the highest-frequency rails. Silicon capacitors solve this by sitting embedded in the bridge, interposer, or ABF substrate.
Three design wins drive the demand step-change:
- Google v8e TPU (2H 2027 launch) — EMIB substrate with embedded silicon capacitors
- Intel EMIB scale-up starting 2027 — covers Microsoft Maia, Amazon Trainium, NVIDIA networking, and Intel's own products
- Amazon Trainium/Inferentia using EMIB — pulls in silicon cap content via Intel
The supply side
Four qualified suppliers: Murata (acquired IPDiA 2016, production in Caen, France), Samsung Electro-Mechanics (in-house), AP Memory (Taiwanese, TSMC fab partnership), and TSMC itself (Integrated Passive Devices on advanced nodes). Murata and TSMC have internal demand from their own packaging activities, leaving SEMCO and AP Memory as the merchant suppliers with most addressable external order book.
SEMCO specifically
Citi: silicon capacitor revenue W609bn FY27E / W905bn FY28E, anchored by W1.6T 2-year supply order Jan 2027 - Dec 2028 from "major global company" (likely Google v8e). Already supplying Marvell (The Elec May 20).
At current SEMCO market cap W140T, the silicon capacitor business is small but high-margin. A sum-of-segments framework that breaks out MLCC + FC-BGA + silicon capacitor + camera modules + net cash lands at gross SOTP of W60-63T (implied price ~KRW 825-870K) under moderate assumptions. Under aggressive bull case (silicon cap scales to W2-3T by FY29-30, FC-BGA gets full TSMC multiples), implied price reaches ~KRW 1.25M — still 32% below current KRW 1.85M.
AP Memory
Core business is PSRAM and high-speed SRAM for wearables/IoT. Silicon capacitor exposure is via TSMC packaging relationship. Needs deeper research before sizing.
Update 2026-05-28 — Full profile written: 6531. Silicon cap exposure is REAL and disclosed (not speculative as initially flagged). Two product lines: discrete S-SiCap IPD (Gen3 in production, Gen4 ramping 2026) and silicon-capacitor interposer IPC (four-reticle mass production from end-Q3 2025). Intel EMIB first-qualified-supplier May 21 2026 with Q2 2026 shipment start — serves Google v8e TPU (2H 2027), Microsoft Maia, Amazon Trainium. CoWoS-S (IPC) + CoWoS-L (IPD) adjacency at TSMC is ADDITIVE. Silicon cap est. 15-25% of FY2025 NT$5.67B revenue (segment split NOT officially disclosed — disclosure gap is the #1 valuation risk). Stock NT$1,080 = +365% in 13 months / +160% in 8 weeks / 42x fwd PE / +39% above MS raised PT NT$777. Verdict PASS at NT$1,080 / WATCH NT$650-800 / BUY NT$400-550.
Open questions
AP Memory's actual silicon capacitor revenue exposure (Zephyr names them but doesn't quantify)Closed 2026-05-28 — see 6531: est. 15-25% of FY2025 NT$5.67B revenue, ramping fast (Q1 2026 total rev +115% YoY); Intel EMIB first-qualified-supplier with Q2 2026 shipment start; CoWoS-S/L adjacency additive. Mgmt does NOT publish segment split — that's the remaining gap.- TSMC's own silicon capacitor business sizing (sold as part of foundry package, not separately reported)
- W1.6T order customer identity (Google v8e most likely per Jukan's EMIB reporting)
- Silicon capacitor margin profile within SEMCO (assumed 30% NI; Citi may have specific guidance)
Cross-references
- MLCC sector deep-dive:
~/claude/output/handoff/mlcc-sector-deep-dive-handoff.md - Capacitor Dossier:
KB/raw/mlcc-research/capacitor-dossier-2026-04.pdf(Embedded Capacitor section pp 11) - Dongguan Securities Chinese MLCC initiation:
~/claude/output/sectors/dongguan-mlcc-initiation-2026-03-25.md - SEMCO swarm files:
~/claude/output/{profile,deep-dive,mgmt-dd,checklist}/009150-ks-*.md