The substrate cycle, dated: what a third of Soitec’s revenue leaving tells you

I. What an engineered substrate is, and why it is a chokepoint

A logic fab converts a wafer into circuits. Soitec makes the wafer that arrives — not a plain silicon disc, but a laminate: a thin, precisely-terminated device layer transferred onto an insulating or carrier base, bonded and split by the company's Smart Cut process. The engineering value is not in the silicon; it is in the interface. Layer thickness uniformity measured in atoms, buried-oxide integrity, defect density and edge behaviour decide whether a customer's process window closes at all.

That is why substrates are a chokepoint rather than a commodity. A radio-frequency front-end designer who has qualified a substrate platform has spent years of process characterisation doing it; changing supplier means re-qualifying the product, not re-issuing a purchase order. The switching cost is the moat — and it cuts both ways. When end demand collapses, the substrate maker cannot pivot into an adjacent market in a quarter, because the adjacent market has not qualified it either.

Soitec's own product taxonomy makes the dependency legible: RF-SOI and POI for mobile front ends, FD-SOI for low-power digital, Photonics-SOI for optical interconnect, imager substrates, and SmartSiC for power electronics in electric vehicles. Four of those families crossed roughly US$100 million¹ of annual revenue (the company reports these platform thresholds in US dollars) by FY2025, when POI became the fourth to do so (Soitec, 27 May 2025). Diversification, in a substrate business, is measured in qualified platforms — and it takes a decade.

II. The cycle, dated

Read in sequence, the filings are unambiguous. On 14 February 2025, nine-month FY2025 revenue was reported down 13% to €564 million, with the deterioration attributed to the automotive market (Le Dauphiné Libéré, 14 February 2025). On 27 May 2025 the company closed FY2025 at €891 million, −9% both reported and at constant currency and perimeter, with Q4 revenue of €327 million, stable year-on-year at constant perimeter, and positive free cash flow of €26 million (Soitec, 27 May 2025). The same release withdrew the company's financial outlook, citing reduced visibility (Boursier.com, 27 May 2025).

Six months later the trough arrived in full. H1 FY2026 revenue, for the half ended 30 September 2025, was €231 million, down 32% reported and 29% organically; Q2 alone was €139 million, up 47% organically on the previous quarter but down 36% against the €217 million of Q2 FY2025. EBITDA fell 30% to €79 million, even as EBITDA margin rose to 34.1% — a combination that tells you the cost base was defended while volume left. The net result for the half was −€67 million, affected by non-recurring items (Soitec, 19 November 2025; Boursier.com, 19 November 2025).

FY2026 closed on 27 May 2026 at €592 million, −34% reported and −30% at constant perimeter and currency (Soitec, 27 May 2026). In two fiscal years, a company that had been guiding toward growth had shed roughly €300 million¹ of annual revenue.

III. What the market did to the equity

Equity markets price substrate cycles violently, because the operating leverage runs in both directions. On 6 February 2025, after a profit warning on FY2025 and a weak indication for FY2026, the shares fell around 28.9% intraday to €58.40, touching €55.70 (Le Revenu, 6 February 2025). On 28 May 2025, the session after guidance was withdrawn, the stock fell again — Les Echos reported a decline of about 20%⁹ and BFM Bourse reported 23%. We give the range rather than pick a number, because the two reputable accounts of the same session do not agree, and rounding a contested figure into a single one is how a dossier becomes a rumour.

IV. The product truth: four lines above scale, one line stopped

The most instructive disclosure of the cycle is not a revenue number; it is a discontinuation. In its FY2025 results Soitec announced a programmed phase-out of Imager-SOI, noting that Q1 FY2026 revenue would be affected and citing US$25 million of Imager-SOI revenue in Q1 FY2025 (Soitec, 27 May 2025). By the November 2025 half-year release, the phase-out was described as an arrêt programmé, and the company noted that excluding the discontinued line, Edge & Cloud AI division revenue rose 34% (Soitec, 19 November 2025).

That is a portfolio decision made in public: stop a line that no longer earns its cleanroom time, and let the mix carry the story. It is also the clearest evidence available that the downturn was not uniform. Mobile and automotive end markets fell; optical and AI-adjacent substrate demand did not.

V. Bernin 4 and the silicon-carbide bet

Capital expenditure is the most honest signal a manufacturer emits, because it cannot be revised in a press release. Soitec began building a fourth plant on its historic Bernin site in March 2022, announcing at the time that it was dedicated mainly to new silicon-carbide substrates and came with a plan to recruit 400 new employees (Le Dauphiné Libéré, 11 March 2022).

The plant was inaugurated on 28 September 2023. Soitec's own release describes a new Bernin plant producing SmartSiC substrates for future generations of electric vehicles, with a 2,500¹ m² footprint, capacity of 500,000¹ wafers per year, and 400 direct jobs created (Soitec, 28 September 2023). The French Ministry of the Economy recorded the same date, with the inauguration performed by the then industry minister (presse.economie.gouv.fr, 28 September 2023). A widely-cited investment figure of €380 million¹ comes from press coverage of the inauguration (Les Echos) and does not appear in Soitec's own release text; we attribute it to the press, not to the company.

The industrial logic was sound and the timing was unlucky. SmartSiC is a power-electronics platform whose demand curve is bolted to European electric-vehicle volumes, and those volumes decelerated exactly as the plant reached readiness. Two partnerships anchor the platform: a cooperation with STMicroelectronics on silicon-carbide substrate manufacturing technology announced on 1 December 2022, under a memorandum of understanding the board authorised on 23 November 2022; and a joint development agreement with Resonac of Japan announced on 24 September 2024 (Soitec/press, dates as given). Neither has been superseded by any disclosure we could verify.

VI. Customers, consortia and the wider corridor

Soitec's commercial history is a list of platform qualifications. The POI franchise traces to a business agreement with Qualcomm Technologies announced on 7 July 2020 for piezoelectric-on-insulator substrates used in 5G RF filters. Capacity outside France matters as much: the company broke ground on an extension of its Pasir Ris fab in Singapore, intended to roughly double annual output at that site toward two million 300 mm SOI wafers a year. The groundbreaking is dated in Soitec's own document repository to early December 2022; because we could only infer the exact day from the document's filename rather than read it in the body, we date it to that month and say so.

Downstream, the Grenoble corridor supplies its own demand. GlobalFoundries and STMicroelectronics finalised their agreement for a jointly-operated 300 mm facility at Crolles on 5 June 2023 — a few kilometres from Bernin. That is ecosystem context, not a Soitec transaction, and we present it as such.

On public money, we are deliberately narrow. The European Commission approved up to €8.1 billion¹ of support from fourteen member states for an IPCEI in microelectronics and communication technologies on 8 June 2023, and France announced twelve validated national projects the same day; Soitec appears on the IPCEI programme's own partner listing. No page we opened states a euro amount allocated to Soitec individually, so this dossier states none.

VII. The human cost, dated

The part of a downturn that reaches families arrives later than the part that reaches share prices. On 29 October 2025, Place Grenet reported that a short-time working scheme was being prepared for the Bernin site; La Tribune reported on 31 October 2025 that the measure would cover the site's roughly 1,800 employees from 17 November 2025. VIPress reported on 3 November 2025, citing the company's CGT union, that the scheme was expected to run from mid-November 2025 to mid-May 2026, and that the group had committed not to pursue economic redundancies during the period.

The commitment was kept in form. What followed was not a redundancy plan but a voluntary one: on 23 April 2026 Place Grenet reported, on the union's account, that management was considering a rupture conventionnelle collective — a negotiated collective-departure scheme — after the short-time working period. The CGT Soitec branch subsequently published, on 20 July 2026, that it had signed the RCC agreement following a consultation of employees. Both of those are union-reported facts and we label them as such; we found no company release stating a target number of departures, and we therefore give none.

For headcount, we use the audited document. Soitec's 2024-2025 Universal Registration Document reports a total workforce of 2,252¹, of which 1,809 in Europe and 1,791 in France. It gives no Bernin-only figure. Press accounts of the site range from about 1,690 to 1,800 depending on the month and the outlet; that is a range, and we publish it as one.

VIII. Governance: a founder-era company hires a sector operator

On 1 October 2025, Soitec announced that chief executive Pierre Barnabé had informed the board of his intention to leave for personal reasons, and opened a succession process. On 8 January 2026 the board appointed Laurent Rémont, effective 1 April 2026 (AFP via Boursorama, 8 January 2026; Electroniques.biz, 9 January 2026). Le Figaro framed the appointment on 12 January 2026 as the recruitment of a sector specialist to rescue the manufacturer.

The sequencing is worth noting for anyone reading this as a career decision: the succession was announced during the short-time working period and completed a month before the RCC discussions surfaced publicly. Leadership transitions in capital-intensive manufacturing are rarely neutral for organisation design.

IX. The turn

On 22 July 2026, Soitec reported Q1 FY2027 revenue of €113 million, up 23% year-on-year at constant currency and scope — the first year-on-year growth in the sequence. On 2 September 2026, in a business update, the company raised expected Q2 FY2027 growth to around 50%, from around 30%, citing strong Photonics-SOI demand.

Two observations, both disciplined. First, the growth is arithmetically flattered by an extraordinarily weak base: €113 million is a recovery against a collapsed comparator, not a return to FY2025 scale. Second, the driver has changed identity. The company that entered the downturn as a mobile-and-automotive substrate supplier is exiting it with optical interconnect — the physical layer of AI data-centre networking — as the stated reason for its raised guidance. If that persists, the strategic description of Soitec changes, and so does the skills profile it buys. That is the subject of the companion dossier in this series.

X. What we deliberately do not claim

We do not claim Soitec silicon is inside any specific consumer device. A widely-circulated March 2026 report attributing an iPhone 17 millimetre-wave antenna module substrate to Soitec rests on teardown analysis relayed by financial media, with no confirmation from either company. Supply-chain attribution of that kind is commercially sensitive and we exclude it.

We do not state a Soitec-specific France 2030 or EU Chips Act subsidy figure, because no primary page we opened contains one.

We do not characterise the SmartSiC ramp. No document we verified states whether the silicon-carbide line is ramping, paused or impaired, and no impairment charge tied to it was found. Silence in the filings is not evidence of either outcome, and we decline to fill it.

We do not give a Bernin site headcount as a point estimate, nor a number of RCC departures, nor an exact percentage for the 28 May 2025 share-price fall. Where reputable sources disagree or fall silent, the disagreement is the finding.