Into Q4.
Okay. Q3, our revenue has been mainly driven by the usual seasonality of personal electronics, where we have benefited of both our increasing content with our main customer and the usual seasonality of the start of the new device. Personal electronics grew 40% sequentially in Q3. Except automotive, I will come back on it, all the other segments grew sequentially, and good news year-over-year. On automotive, we are still on a year-over-year decrease, but the main gap is related to one customer specific an electric car maker, well-known. You know, that forestry, the progressive decrease of the fees related to capacity reservation.
Clean of this effect that is not product-related, that is, more, let's say, the heritage of the shortage period. We can say that automotive is starting to grow year-over-year, very, very close. This was the main point of Q3. The book-to-bil l was basically above one, which was also good for Q4.
Yeah. Maybe just keeping on Q4, obviously, you guided sales, I think, $3.28 billion for Q4, slightly above the - 10% that you would see for seasonality. Maybe help us understand, does that help us appreciate what the run rate will be into 2026? And again, as reference to automotive, how should we think about that as we go into 2026?
It's a very interesting question. 2026 . Clearly, again, the usual seasonality for, for ST is to have a first quarter - 10% or slightly above - 10%, mainly driven by the personal electronics and the Asia, because of the Chinese New Year impact for mass market and distribution. Today, the dynamic of our backlog coverage for Q1, linked to the order entry we have, is clearly securing ourself that we will be capable to deliver -10% to -11% in term of revenue Q1, which is a positive news, confirming that we are basically almost free of material inventory correction. That was the case in Q1 last year. By the way, if we deliver - 10% to -11% Q1 versus Q4, year-over-year will be a nice 20% growth.
Q1 2026 versus Q1 2025. This is what we can see. Qualitatively or directionally for next year, what will be the main contributor of the growth of ST above the cycle? First of all, will be a massive introduction of new product on microcontroller. Clearly, next year, because now we are inventory-free, in terms of adjustment on distribution, industrial, we will have a legacy growth. More important, we will introduce basically almost 45 new products on micro next year at 40 nanometer or even 18 nanometer. Micro, which will be fitting with the demand, okay, to have more computing power, more memory storage, hardware accelerator for AI at the edge, and so on. Clearly it will be one positive growth driver. Second positive growth driver will be analog.
Why? Because analog, and spread between personal electronics, automotive, and industrial. Why? Because here is, is mainly for personal electronics new product, and for industrial and for automotive, it is, let's say, the moderate growth, okay, we are seeing on the market, and clean of inventory correction. As usual, forestry, you have the engaged customer program, LOHER sold by Satellite , with our new customer, ADAS system. Personal electronics will be with our main customer more moderated, but this is, okay, what we see as a growth driver. The detractor will be the capacity reservation fee that will be basically close to zero. At the end, we are not yet in position to confirm exactly the percentage of growth we have, but we can say Q1 has a seasonality. We enter in the year with Q1 20% growth year-over-year, so we can expect a growth next year.
Very clear. Very clear. Maybe take a little bit of a detour here and just ask about AI servers. Obviously, a peer is reporting this morning a doubling of sales into next year. I know you've got ambitions to get into power supply units, particularly using, I imagine, silicon carbide, silicon carbide modules, but you have the tie-up with Innoscience as well. Maybe help us understand how that opportunity plays out for ST, when would that come in, and could that be a contributor in 2026?
Of course, I have seen, like you, the result and guidance, and communication of our competitor. What is the difference between this competitor and ST? What we have, what he has not, and what he has, what we have not. Okay. What we have and what he has not, we have today now the silicon photonics that will start to contribute with the switch from copper cable communication connectivity to optical, let's say, receiver and transceiver. This forestry will be a growth that should bring us a revenue contribution in three years about $300 million and five, at least $500 million at the end of the decade. What we have is our general -purpose microcontroller that are spread everywhere in the rack.
What we have as well, but not yet present because we focus on other markets like the automotive, is a switch on silicon carbide, and what we are introducing is switch on GaN. What we have not yet is a low-voltag e capability on MOSFET or on a smart power switch. We are working now to do it with a next generation of 800-volt architecture. To make a long story simple, ST, revenue in server in the short term, so mid-thirty-six, twenty-eight, will be mainly driven by silicon photonics, and, and, and microcontroller, and more marginally, I have to say, by power and analog. That will start out to be boosted beyond 2027, 2028, by the new architecture.
This is the path of ST on AI server. Why we are not present? Okay. It was a strategic choice, mainly power, automotive-oriented and less industrial or infrastructure. This is the situation we have to deal with.
Gotcha. Appreciate that. On short notice to answer that question. Maybe if we jump back to, to silicon carbide, I mean, we did see revenues of $1.1 billion in 2024. And I think you said this is a transition year 2025, and but 2026, maybe 2027, we get back to that sort of levels eventually. But maybe help us understand the profile and the demand, perhaps, by region, Europe and China, in particular.
Clearly, you know, ST has been really successful on silicon carbide, mainly driven by one customer. We started, let's say, not late, but we started in the past two years, the diversification with European first and targeting the China market after. It's clear that in 2025, when you accumulate, our main customer decrease and correcting inventory massively.
Plus, the European player struggling more in, in their capability to grow, and with the Chinese success, but with a strong price pressure, at the end, okay, 2025 is a significant year of decrease. How have we reacted in front of this situation? First of all, we reacted, okay, since many quarters to diversify and accelerate ourself both in Europe and in China. Next year, we will grow significantly, well above $100 million , compared to this year. 60% will be driven by this time, the start of the European program, 40% by the Chinese one.
Gotcha.
Moving forward, we expect to go back to the peak of our revenue in 2024, in 2027, and directionally go to the $2 billion between 2028, 2029.
Gotcha. Very clear. Maybe if another area that investors are interested in is, you know, the power discretes area, power indiscrete. Your operating margin was weak, I think - 15%, last quarter. You know, we're seeing that inventory normalization coming through the second half of 2026, and you've got the manufacturing reshaping program as well. How does that all drive profitability or the regain of profitability in that space?
In a consistent way, we communicate that our reshaping plan, so cost-based resizing and manufacturing reshaping. Yes, the cost-based, the operating expense, okay, contribute now, okay, it's $120 million less, per year starting 2025, 2026, 2027. Unfortunately, on manufacturing, okay, the contribution will be 2027. Why? Because in 2025, it was the year to prepare the technology transfer, product qualification, and here we are not completely controlling the agenda because it's customer, we control the agenda. Entering in 2026, we have to ramp down the fab we want to close, and we have to ramp up the fab we want to open. Especially on the silicon carbide and on, on power overall, we will be at a period of time where the 6-inch will start to degrade their performance.
Sort of, you know, just a change to the plugins on the, in the interconnect.
No, I mean, we claim that on power, power and analog, okay, we want to reach 10% market share . That of this addressable market, that the overall content on the AI server, addressable by ST, is $2,000 of components. Out of which you have a 500, on silicon photonics . And the rest is power analog and microcontroller . So on this power analog, microcontroller, we want to achieve 10% of market share . Okay. On silicon photonics, who are our competitor? Is Tower Semiconductor and GlobalFoundries. Okay, of course, I have a huge respect for this company, but Tower Semiconductor is on eight-inch silicon photonics. We are on 1 2-inch. Okay. I do not know how Tower Semiconductor will move to 12 -inch without an agreement .
For sure, okay, on silicon photonics, I expect our market share to be well above 10%. That will benefit to the growth of ST.
Gotcha. Very clear. I think maybe just on GaN as well, 'cause I do think it's a very interesting tie-up with InnoScience, given your pricing power, given you sort of regional prowess as well. Also, there's a systematic change in the data center. I think your interim bus conversion's moving to GaN or your second stage. Yeah. That feels as though it's a market that's ready for you guys to address. Is that part of the long-term plan, sort of 2027 and beyond, when we get Khyber Racks?
No, it is clearly part of our plan. Sure. It is, it is, I repeat, okay, compared to the big competitor, Infineon and MTS. Okay. Our focus using wide bandgap technology like silicon carbide or GaN, were more exclusively driven by automotive. Up to two years ago. Okay. Two years ago, I decided to break it. Okay. And that is the reason why I changed organization, I say I want to have product organization not driven by automotive. But more broad range. Okay. So these two blocks, analog power sensor and micro and digital, and to support the four segments in order to diversify ourself. Not because I was anticipating a disaster on automotive, but I was feeling that is the protection of the company to be well balanced. Unfortunately, we know what happened with automotive that will come back.
For the time being, it's a little bit struggling. Yes, okay, we will participate in this market. The point is today we are not participating because you have already two or three players in good position. We have to prepare the next step, because if not, we will come with incumbent position. We will have to pay the margin for sure. It's better to play the next step, which will be the 800 -volt architecture, and when our product will be ready. Either our SiC, our GaN, but the low voltage, so the low voltage MOSFET and the smart switch, smart power switch that we have not yet developed, because automotive focus.
Gotcha. Okay. That's pretty clear. Maybe one last one from me, just on the gross margin guidance for Q4. You know, I think you guided at 35%, including the 290 basis points headwind on unused capacity charges. I think there's an additional 30 basis points. I'm reading this from a sheet of paper. So, 30 basis points with process migration. I could almost pass this to you, actually. Really, just how should we think of the evolution on unused capacity charges as we go through next year?
That next year will not completely disappear. For sure, we'll be at least, we expect, compared to Q4 this year, at least divided by two. In terms of negative contribution to the gross margin, moving forward. Mainly, Crolles 300 will be number, with unused cost, I guess. Agrate as well. Silicon carbide, we will close the six-inch . So we'll set up just what we need in terms of capacity on eight -inch.
We will have still maybe some legacy capacity available on eight -inch that will generate unused capacity cost still Q4 2026. I hope at least divided by two, yeah, compared to Q4. This is all we see moving forward, and of course, will be related to the revenue we will have in H2 next year and in H1 in 2027.
Jean- Marc, I see the clock ticking down. Thank you very much for coming. Enjoy Barcelona. Thank you.
Thank you very much. Thank you. Thank you.