ROHM

Phase A — Understand the business

Company Overview

ROHM is a ~¥480B-revenue ($3.2B) integrated device manufacturer (IDM) founded in Kyoto in 1958 by Kenichiro Sato — who started by inventing a small precision resistor in 1954 and built it into a global semiconductor house. It designs, fabricates, and sells its own chips (IDM, not fabless) across four reported segments:

• LSI — analog & mixed-signal ICs (power-management ICs, motor drivers, op-amps, LED drivers, sensors), plus LAPIS microcontrollers/memory. ~¥55B/quarter run-rate (largest segment).
• Semiconductor Devices (Discrete/Power) — the strategic engine: diodes, transistors, and the crown-jewel SiC (silicon-carbide) MOSFETs & modules, Si IGBTs, GaN. ~¥56B/quarter, growing +19% YoY.
• Modules — power modules, optical modules, printheads. The laggard (~¥8B/quarter, flat-to-down).
• Other — foundry, tantalum capacitors (the historical resistor/passives roots), thermal printheads.

The business model in one line: ROHM sells the "energy-saving + downsizing" analog and power layer that sits between a battery/grid and a motor/processor — the boring-but-critical silicon that switches and regulates power. Its self-declared vision is "power and analog solutions".

Contract structure: classic broad-line semi — no take-or-pay, no single mega-contract; revenue is a long tail of automotive OEM/Tier-1 design-wins (multi-year, sticky once designed-in) plus catalog/distribution volume. Payment terms are ordinary trade, not recurring/subscription. Concentration is by end-market, not by single customer (see Lens 4).

Supply Chain

ROHM is unusually vertically integrated for its size — a deliberate strategic choice that is the whole SiC story. Named map, upstream → downstream:

• Upstream (materials): For SiC, ROHM owns SiCrystal GmbH (Germany) — an in-house SiC boule/substrate maker acquired 2009. This is the single most important node: it means ROHM is one of very few players (with Wolfspeed and STMicro) that controls its own SiC wafer supply rather than buying substrates on a market where prices just collapsed. For silicon wafers, standard Japanese/global suppliers (Shin-Etsu, SUMCO). Gold/copper for packaging — a real cost line (material costs +¥12.8B YoY partly on gold prices).
• The company (fabs): In-house wafer fabs and assembly across Japan (Kyoto, Shiga, Fukuoka) + overseas back-end (Philippines, Malaysia, China, Thailand). The strategic new node: Kunitomi plant, Miyazaki (the ex-Solar Frontier / Apollo site) — ROHM's flagship SiC fab, mass-production of SiC power devices from April 2026.
• The Toshiba tie-up (chokepoint-sharing): Dec 2023, ROHM + Toshiba agreed a ¥388.3B joint investment (ROHM ¥289.2B into SiC at Kunitomi; Toshiba ¥99.1B into Si at Nomi), backed by ¥129.4B METI subsidy — an explicit Japanese-government bet to keep power-device capacity onshore. ROHM separately holds a legacy stake in the Toshiba take-private consortium (JIP).
• Downstream (customers): Automotive OEMs and Tier-1s (Denso-type integrators, EVEnterprise valueWhat it would cost to buy the whole company: its market value plus its debt, minus the cash you would get with it. Often very different from market cap. inverter makers) — automotive is ~49% of revenue. Industrial (factory automation, motor drives), consumer, and now AI-server / data-center power (BBU/PSU makers) — the new demand vector.

Chokepoints / single-source: ROHM's own SiCrystal substrate line is both a moat (self-supply) and a risk (it built 6-inch capacity into a market that moved to 8-inch and then oversupplied — the direct cause of the impairment). Distribution runs through the big global cats (Digi-Key, Mouser, Arrow) plus direct.

Competitive Advantages (moats)

Where the moat is real:

• SiC vertical integration + first-mover IP. ROHM claims the world's first mass-produced SiC MOSFET (2010) and is on its 4th-generation device, designed into numerous EV and industrial platforms. Owning SiCrystal (substrate) + wafer + device + the analog control IC around it is a genuinely rare full-stack position — only Infineon, STMicro, Wolfspeed and onsemi sit in the same tier; the top-5 control >90% of SiC revenue.
• Analog + power co-design. ROHM is one of few that can pair the power device with the control/gate-driver IC in-house — a real system-level switching-cost advantage in automotive, where a validated device+driver+module package is designed in for the model's life (5–7 yr).
• Automotive qualification moat. Auto design-wins are slow, audited, and sticky. ROHM's ~49% auto mix is a durable annuity once won.

Where the moat is weaker than bulls think:

• Scale disadvantage. ROHM ($3.2B revenue) is a fraction of Infineon ($18B) and STMicro. In a capacity/price war, the biggest balance sheet wins — and ROHM just proved it by taking the impairment first.
• SiC is no longer scarce. The differentiation that justified the SiC premium is eroding as Chinese substrate makers flood the market (see Lens 12/13). Being #5 in a commoditizing niche is not a moat.
• Bargaining power: modest. Against giant auto Tier-1s and hyperscaler-adjacent PSU makers, ROHM is a qualified-but-substitutable supplier; against Chinese SiC entrants, it competes on price it can't win.

Segments

By business segment (Q3 of the year ending March 2026, i.e. Oct–Dec 2025 quarter — the cleanest recent split):

Full-year (ended March 2025) segment growth: LSI +7.1%, Semiconductor Devices +9.7%, Modules +3.0%, Others +3.6% — a broad, unspectacular recovery masking the SiC write-down beneath it.

By end-market (year ended March 2025): Automotive 49.2%, Consumer 21.9%, C&S/Components-&-Systems 12.3%, Industrial 12.7%, Communication 3.8%. The trajectory that matters: automotive has climbed from ~45% (FY-ended-Mar-2023) to ~49% — ROHM is levering itself into EV/auto power right as the EV growth curve flattened. That is the crux of the whole thesis.

No our figures on the shelf — every number here is, not.

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Phase B — Measure performance

Earnings Result

The defining print — year ended 31 March 2025:

The story is unmistakable: operationally roughly break-even, but a ¥163.2B SiC impairment turned it into a ¥158B net loss — one of the larger single write-downs by a Japanese semi in the cycle. ROHM's own stated cause: "slowdown in BEV market growth and the rise of Chinese manufacturers," plus "excess investment" and declining demand for 6-inch substrates. Translation: ROHM built SiC capacity (6-inch) for an EV ramp that decelerated, into a market that then oversupplied and moved to 8-inch — and wrote off the mismatch.

Current year (ending 31 March 2026) — mid-recovery, but guidance walked down twice:

• 9M (Apr–Dec 2025): net sales ¥369.5B, net income ¥14.8B, basic EPS ¥38.4 (vs ¥0.55 prior-year 9M).
• Q3 (Oct–Dec 2025) alone: revenue ¥125.2B (+11.2%), operating profit only ¥2.0B, net profit ¥4.5B — thin operating margin because "temporary quality-assurance costs for SiC devices" hit as SiC scaled into auto inverters.
• Guidance trajectory (the tell): initial full-year revenue ¥510B → revised to ¥480B → ¥460B; net income guided to just ¥9.0B. Revenue held up (forex tail: assumed ¥153/USD lifted sales ~¥20B), but profit guidance was cut hard on SiC costs and gold-price material inflation (+¥12.8B).

Balance-sheet flags (as of 31 Mar 2025): Total assets ~¥1.12T, total equity ~¥915B, total debt only ~¥40B → net cash position, equity ratio very high (~80%). This is the single most important defensive fact: ROHM took a ¥163B hit and its balance sheet barely flinched. A fortress balance sheet is why the equity survived the write-down.

Market reaction: not a crash — the opposite. The stock is at an all-time high (see Lens 8). The impairment was treated as a kitchen-sink event that clears the SiC overhang; the market is now paying for the recovery + AI-server optionality.

Earnings Calls (sentiment trend)

No transcripts on the shelf; sentiment reconstructed from earnings briefs + IR materials. The tonal arc across the last ~4 quarters:

• Early/mid FY-ended-Mar-2025: defensive — inventory correction, weak consumer, "adjusting SiC investment pace." Management signalling caution and cost discipline.
• Impairment quarter (reported May 2026 for FY-end Mar-2025): confessional — explicit acknowledgment of "excess investment," BEV slowdown, Chinese competition. The rare Japanese-management move of taking a big, honest write-down rather than dribbling it out.
• Q3 (ended Dec 2025, reported Feb 2026): cautiously turning — automotive "strong recovery" (+13.9% auto revenue YoY, +¥7.9B profit contribution), but hedged by "temporary quality-assurance costs." Management stopped talking down SiC and started talking up AI-server / HVDC power — a deliberate narrative pivot from "EV SiC" (broken) to "AI-power SiC" (new).

Phrases that appeared: "800VDC / HVDC," "AI server," "battery backup unit (BBU)," "power + analog." Phrases that receded: the aggressive "6.5×/35× SiC capacity" ramp targets from the 2023 Toshiba announcement — quietly de-emphasised. The stopped-saying is as informative as the started-saying: ROHM is re-badging the same SiC capacity from an EV story to an AI story.

Comps

Global power/analog peers. Multiples are with source/date; where I could not source a figure it is n/a (never fabricated).

Read: ROHM is the smallest of the credible power-semi set — ~1/8th of Infineon, ~1/2 of Renesas. On EV/EBITDA (23.5x) it sits mid-pack, richer than onsemi/STM, near Renesas, cheaper than Infineon — but that is on depressed EBITDA (a near-break-even operating year). Its market capMarket capitalisationThe share price multiplied by the number of shares. What the market says the equity is worth. doubled in a year (stock +241%), so the "cheap Japanese small-cap" framing is gone; ROHM is now priced as an AI-power growth name, not a cyclical laggard. ROE −4.5% is the ugly number — even in a loss year, it flags that ROHM's capital efficiency has lagged peers for years, not just this cycle.

Stock-Price Catalysts

ROHM has round-tripped violently. Key moves:

• All-time TSE high ¥5,950 (closing 3 Jul 2026); intraday all-time high ¥5,752 was 3 Jun 2026 — the stock made new highs repeatedly through mid-2026.
• +14.18% in one day (3 Jul 2026), close ¥5,950 (+¥739) — the single biggest recent catalyst: JP Morgan kept Overweight and DOUBLED its price target from ¥3,900 to ¥8,000, citing SiC demand for AI servers/data centers, not just EVs, expanding "faster than expected".
• +241.6% over the trailing year — a full re-rating off the impairment low.
• Beta 0.45 — historically a low-beta defensive Japanese name; the recent moves are idiosyncratic (SiC/AI narrative), not market-driven.

What the pattern reveals: ROHM's stock is now a pure-play sentiment vehicle on the SiC narrative. It sold off through the EV-SiC disillusionment (2024–25), bottomed on the impairment, and has exploded on the AI-server-SiC re-rating (2026). The market reacts to (1) the SiC demand narrative (which end-market is buying), (2) sell-side price-target resets (the JPM double), and (3) forex (¥/$). It does NOT trade on the current P&L — which is still barely profitable. This is a story-ahead-of-numbers stock.

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Phase C — Judge people & books

Management

• CEO transition (fresh). Isao Matsumoto (long-time president/CEO) resigned as director effective 31 Mar 2025; Katsumi Azuma became President (Representative Director) & CEO in April 2025. The impairment and the AI-pivot are effectively the new CEO's opening act — a classic "new boss clears the decks with a big write-down" dynamic. Track record of Azuma specifically: thin public record; assess on the next 2–3 prints.
• Founder legacy / ownership archetype. Founder Kenichiro Sato led ROHM for >50 years, died Jan 2020. The company is a "family control without ownership" case (studied academically as exactly this archetype ): the founding family's direct stake is now low-single-digit/below-threshold, but influence persists through the Rohm Music Foundation (10.76% holder) and the conservative Kyoto-IDM culture. Top holders: Master Trust Bank of Japan 14.84%, Rohm Music Foundation 10.76%, foreign ~36.4%, treasury ~6.3%. No single controlling shareholder.
• Capital-allocation history — the honest verdict is mixed-to-poor. The ¥289B SiC/Kunitomi bet (Toshiba tie-up) is the defining allocation call of the decade, and it produced a ¥163B impairment before it produced a profit — capacity built ahead of demand into a price war. Set against that: a fortress net-cash balance sheet (only ¥40B debt on ¥1.1T assets), a maintained ¥50 dividend through the loss, and treasury buybacks (6.3% held). ROE −4.5% (and structurally low even in good years) says the core problem: ROHM hoards capital and earns a low return on it — the opposite failure mode from over-leverage. It is over-capitalized and under-returning.
• Red flags: the SiC over-investment is the big one (a genuine mis-forecast, now owned via the write-down). No promotional behaviour, no obvious related-party abuse. The Music Foundation stake is a legacy quirk, not a governance abuse. Standard Japanese cross-shareholding/low-float dynamics apply.
• Archetype: conservative professional-management IDM under a new CEO, still shadowed by founder-era Kyoto culture. Implication: unlikely to do anything reckless with the balance sheet; also unlikely to move fast or return capital aggressively. Steady hands, low urgency.

Forensic Red Flags

Web-only; no filings on shelf to line-check. Accounting-risk read is directional.

• The impairment is the headline forensic event — but it's a "good" one. A ¥163.2B write-down of SiC fixed assets is enormous, but it was taken transparently and up-front (kitchen-sink), not smoothed. That is analytically reassuring vs. the alternative (dribbling losses). Watch for: any further SiC impairment if 6-inch/8-inch substrate prices keep falling — the first write-down may not be the last if the price war deepens.
• Non-GAAP / SBC: Japanese reporting relies less on aggressive non-GAAP add-backs than US peers; SBC is not a material flatter here. Low risk.
• Cash vs. earnings divergence: the net loss was non-cash (impairment) — operating cash flow and the balance sheet stayed strong (net cash). This is the correct signature of a real write-down, not an accrual problem. Positive.
• Inventory: management flagged inventory turnover months trending DOWN across LSI/Power/Other — i.e. inventory being worked off, not building. Constructive, not a red flag.
• Material-cost inflation: +¥12.8B YoY partly from gold prices — a real margin headwind, disclosed, not hidden.

Regulatory findings (required sub-section). Per regulatory/regulatory-findings.md: ROHM has no SEC CIK — not an SEC filer, so no EDGAR LR/AAER search is possible (total_sec_findings: 0, which reflects non-applicability, not a clean SEC audit). Non-SEC web search surfaced one material historical finding:

• Electrolytic-capacitor price-fixing cartel (settled ~2016). ROHM Co., Ltd. and ROHM Semiconductor USA were among defendants in the multinational capacitor antitrust matter; ROHM participated in a first-round civil settlement totalling $32.6M in the US direct-purchaser litigation, alongside DOJ criminal pleas by multiple manufacturers and parallel probes in Japan, EU, Korea, Taiwan, China, Brazil, Canada. Resolved, historical, not ongoing — but a real black mark on the passives-era ROHM and worth logging.
• No material recent FTC/DOJ/EU enforcement surfaced against ROHM's semiconductor business as of 2026-07-07.

Verdict: No going-concern or fraud signal. The books tell a clean story of a bad capital decision — the write-down is honest. One resolved historical antitrust settlement (capacitors). Verified via web search + the regulatory-findings file (SEC non-applicable) as of 2026-07-07.

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Phase D — Project & stress-test

Forward Projection

Building bottom-up from the current run-rate. All outputs, inputs labeled. No our model logged (watchlist/unattended run — per skill rules, only log a committed base case). Fiscal years end 31 March; shares outstanding ~386M (ex-treasury).

Anchor: year ending Mar-2026 tracking to ~¥460B revenue, ¥9B net income (¥23 EPS) on guidance; but 9M already did ¥14.8B net / ¥38.4 EPS, implying a soft Q4 or conservative guide.

• Base — modest recovery, SiC stays cost-heavy. FY-end-Mar-2027 revenue ¥490B; op margin recovers to ~6% as SiC quality-assurance costs normalize and Kunitomi (April-2026 start) absorbs → net income ~¥28B → EPS ~¥72. FY-end-Mar-2028 revenue ¥525B, net ~¥40B → EPS ~¥104.
• Bull — AI-server SiC inflects + EV re-accelerates. 800VDC/HVDC BBU/PSU design-wins ramp from 2027, auto SiC re-accelerates; revenue ¥560B+ (Mar-2028), op margin low-double-digits, net ¥55–60B → EPS ~¥145.
• Bear — SiC price war deepens, second impairment, EV stays soft. Substrate ASPs keep falling, Chinese share grabs auto SiC, another write-down; revenue flat ¥455–470B, op margin stuck ~3–4%, net ¥12–18B → EPS ~¥35–45.

The number that matters: at ¥5,950, on base-case ~¥72 FY-Mar-2027 EPS, ROHM trades ~83× forward earnings. Even on a generous bull ¥145 EPS two years out, that's ~41×. The stock is priced for the bull case to be largely correct. There is little valuation cushion if the AI-server SiC ramp slips or a second SiC impairment lands.

Bull vs Bear

Bull case. ROHM is a rare full-stack SiC IDM (owns the substrate via SiCrystal) with a fortress net-cash balance sheet, that has already taken its pain (¥163B kitchen-sink impairment clears the EV-SiC overhang) and pivoted its SiC capacity toward the fastest-growing power market on earth — AI-server / data-center HVDC, where its 750V SiC MOSFET (SCT4013DLL) is already designed into battery-backup units for ±400V/800VDC architectures, with mass production ramping Q2–Q3 2026 and volume peaking 2027. Automotive is recovering (+13.9% YoY), the new CEO has a clean slate, and 92GW of incremental AI-data-center power demand by 2027 is a secular tailwind that needs exactly ROHM's product. If SiC re-rates as an AI-power story rather than an EV story, the earnings base can triple by 2028 — which is what JPM's doubled ¥8,000 target and Simply Wall St's ¥543B-revenue/¥54B-earnings 2028 path encode.

Bear case (2–3 permanent-impairment risks). (1) SiC is commoditizing, and ROHM is #5. Substrate prices collapsed >20% below $500/wafer and now sit near $400 or cost, driven by Chinese overcapacity backed by $15B of state subsidies and BYD-style localization. Being the smallest of the credible players in a price war is a structural disadvantage — the ¥163B impairment may be the first, not the last. (2) The AI-server SiC TAM is real but early and contested — mass production is Q2–Q3 2026 with volume "after 2027," and Wolfspeed, STMicro and onsemi are chasing the same BBU/PSU sockets; ROHM has no disclosed anchor customer yet. (3) Expectations are stretched: the stock is at an all-time high, +241% in a year, ~83× base-case forward EPS, on ~2% operating margins — a story fully priced before the P&L confirms it.

Pre-mortem (18 months out, thesis broke): It's early 2028. AI-server SiC design-wins went to Infineon/Wolfspeed at 8-inch scale; ROHM's 6-inch legacy and sub-scale cost position lost the price war; Chinese SiC took auto share; a second SiC impairment landed; EV stayed soft; the stock round-tripped from ¥5,950 back toward ¥3,000 as the AI-power narrative failed to show up in margins. The tell in hindsight: the market re-rated on a narrative pivot (EV→AI) using the same capacity that had just been written off, and paid an all-time-high multiple for optionality that a bigger, cheaper rival captured instead.

Are multiples too high? On current earnings, unambiguously yes — ~83× base-case forward EPS with 2% operating margins is a growth multiple on a cyclical laggard. Justified only if the AI-power SiC ramp is both large and ROHM-captured.

Contrarian view (what the market refuses to see): The bulls are treating ROHM's SiC capacity as an asset re-pointed at AI. But that capacity was impaired for a reason — it was the wrong node (6-inch) at the wrong scale (#5) at the wrong cost. Re-labeling it "AI-server SiC" doesn't fix the structural cost/scale gap versus Infineon. The market has priced the pivot's upside while ignoring that the same weakness that caused the write-down travels with the capacity into the new market.

Devil's Advocate (short-seller)

Dismantling the bull case. Revenue concentration: ~49% automotive into a decelerated EV cycle — the exact exposure that just caused a ¥163B write-down; if EV SiC stays soft and AI-server volume is "after 2027," there's an air-pocket. Moat weaker than bulls think: the "world-first SiC MOSFET" pedigree is 15 years old; the current fight is about 8-inch scale and cost, where ROHM is sub-scale vs Infineon/STMicro and undercut by subsidized Chinese substrate. Owning SiCrystal is a double-edged sword — it's why ROHM couldn't just walk away from the capacity it had to impair. Most dangerous competitor bulls underestimate: not Infineon (obvious) but Chinese SiC substrate/device makers — they turned SiC into a commodity in 18 months and are localizing the auto supply chain ROHM depends on. Worst capital-allocation move: the ¥289B SiC build-out that produced a ¥163B impairment before a yen of profit — a textbook capacity-ahead-of-demand error, now owned. Assumptions that must hold for ¥5,950: (a) AI-server SiC is large and ROHM wins meaningful share, (b) no second SiC impairment, (c) auto SiC re-accelerates, (d) margins climb from ~2% to low-double-digits. If growth disappoints 20–30%: on ~83× base EPS, a miss re-rates the multiple and the earnings — a plausible path back toward ¥3,000–3,500 (near JPM's old ¥3,900 target). Single scenario that permanently impairs: SiC becomes a fully commoditized, Chinese-dominated component (like solar cells did) and ROHM is stuck as a sub-scale #5 with an impaired asset base and structurally low ROE — a value trap wearing an AI-growth costume.

Management Questions (ordered by information value)

1. Of the ¥163B SiC impairment, how much of the written-down 6-inch capacity is actually redeployable to AI-server/HVDC demand versus permanently stranded — and does the current book value assume a second write-down is off the table?
2. Name the AI-server/data-center customers and platforms where your 750V SiC (SCT4013DLL and successors) is designed in for BBU/PSU — and what is the revenue run-rate you expect from AI-power SiC in the years ending Mar-2027 and Mar-2028?
3. At today's SiC substrate ASPs (~$400/wafer, near cost), what is your gross margin on SiC devices, and at what volume/node (8-inch) do you reach cost parity with Infineon and STMicro?
4. What is your realistic 8-inch (200mm) SiC transition timeline and capexCapital expenditureMoney spent on long-lived things — buildings, machines, servers — rather than on running costs., and how do you avoid repeating the 6-inch capacity-ahead-of-demand error?
5. ROE has been structurally low (−4.5% this year, mid-single-digits in good years) — with ~¥900B equity and only ¥40B debt, what is the plan to raise return on a heavily over-capitalized balance sheet (buybacks, leverage, higher-margin mix)?
6. How do you defend automotive SiC share against subsidized Chinese entrants localizing the EV supply chain — where specifically do you still win, and where have you already lost?
7. What automotive design-win backlog (lifetime revenue) do you hold today, and how has it trended over the last four quarters?
8. The "6.5×/35× SiC capacity" targets from the 2023 Toshiba announcement have gone quiet — what are the current SiC capacity targets, and were the old ones abandoned?
9. What is the Kunitomi (Miyazaki) fab's ramp curve, utilization plan, and breakeven timeline now that mass production started April 2026?
10. How do you think about the ¥50 dividend and buybacks versus reinvestment, given the balance sheet can clearly fund both — is a step-up in capital return on the table?
11. What is your GaN strategy and timeline relative to SiC, given GaN's rise in AI-server/consumer power and reported GaN supply tightness?
12. What forex assumption (¥/$) underlies guidance, and how much of the recent revenue "strength" is volume versus the weak yen (you cited ¥153/USD adding ~¥20B)?
13. What is the current status and strategic intent of your Toshiba relationship and any residual JIP/Toshiba stake — is further consolidation of Japanese power-device capacity on the table?
14. In LSI/analog, where are you winning share, and can analog margins offset SiC's volatility to smooth the P&L?
15. Under the new CEO (Azuma), what is the single biggest strategic change versus the prior regime — and what will you have proven by the year ending March 2028?

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