Douglas R. Bettinger
Executive Vice President, Chief Financial Officer at Lam Research
Excellent. Thank you, Tim. Good afternoon, everyone, and thank you for joining our call today during what I know is a busy earnings season. Before I start, I want to remind everyone that on May 21, 2024, we announced a 10 for 1 stock split which was effective October 2, 2024. All references made to share or per share amounts in my remarks have been adjusted to now reflect the stock split.
We delivered strong results in the September 2024 quarter. Our revenue and earnings per share came in above the midpoint of our guided range, while both gross margin and operating income percentage exceeded our guidance range. I'm pleased with the Company's continued strong revenue and profitability execution, as well as our solid generation of free-cash flows for the quarter, which came in at $1.46 billion or 35% of revenue.
Let's look at the details of our September quarter financial results. Revenue for the September quarter was $4.17 billion, which was an increase of 8% from the prior quarter. Our deferred revenue balance at the end of the quarter was $2.05 billion, an increase of $495 million from the June quarter. This grew mainly due to customer advanced payments. I believe our deferred revenue balance will trend lower into calendar year 2025, but you will likely continue to see fluctuation quarter-to-quarter.
From a segment perspective, September quarter systems revenue in-memory was 35%, roughly in line with the prior quarter level of 36%. Within the Memory segment though, DRAM increased coming in at 24% of systems revenue versus 19% in the June quarter. DRAM spending was focused on technology upgrades to one alpha, one beta, and some initial ramp of one gamma nodes to enable DDR5 and high-bandwidth memory. The non-volatile memory segment represented 11% of our systems revenue, which was down from 17% in the prior quarter. This decline is driven by the timing of one customer's sequentially lower investment in specialty DRAM, that we characterized as a non-volatile investment because it has a non-volatile component in the device.
The NAND segment has experienced a prolonged down-cycle compared to historical norms. However, we anticipate that spending will increase in calendar 2025 as utilization rates improve to more normal levels and our customers begin to invest in conversions to two 256 and 384-layer class devices. The Foundry segment represented 41% of systems revenue, a slight decrease from the percentage concentration in the June quarter of 43%.
In dollar terms, spending was relatively unchanged quarter-to-quarter. The Logic and other segment was 24% of our systems revenue in the September quarter, up from the prior quarter level of 21%. The increase was driven by an uptick in both leading-edge and specialty node logic devices.
Now I'll discuss the regional contribution of our total revenue. The China region accounted for 37%, down slightly from 39% in the prior quarter, and a little bit stronger than we expected. Most of our China revenue continued to come from domestic Chinese customers. And as Tim mentioned, we expect spending from this region will decline in the December quarter, I think perhaps to approximately 30% of December's revenue.
Our next largest geographic concentration was Korea at 18% of revenue in the September quarter, which was flat with the June quarter. And finally, Taiwan and the United States rounded up the remainder of the top four regions. Our customer support business group generated approximately $1.8 billion in revenue for the September quarter, up 4% from the June quarter, and 25% higher than the same period in 2023. The sequential dollar growth was split evenly between Reliant Systems and all other components of CSBG. The spare parts component of CSBG continues to be the individual largest piece of this business unit's revenue.
Let's turn to gross margin. The September quarter came in at 48.2%, which exceeded our guided range. Gross margin decreased a little sequentially, however, reflecting a decline in customer mix, as well as an increase in incentive compensation. These factors were partially offset by improved factory utilization, as we continue to make progress on our operational initiatives. Operating expenses for September were $722 million, up from the prior quarter amount of $689 million. The increase was partly due to growth in program spending, as well as higher incentive compensation tied to the Company's increased profitability outlook. R&D accounted for 67% of the total spending.
Operating margin for the current quarter was 30.9%, slightly above the June quarter level of 30.7% and above the high-end of our guidance range, primarily because of the higher revenue, and continued strong gross margin performance. Our non-GAAP tax rate for the quarter was 13.8%, generally within the range of our expectations. Our estimate is for the tax rate to continue to be in the low-to-mid-teens range in the near term.
Other income and expense for the September quarter came in at $13 million in income, compared with $19 million in income in the June quarter. The decrease in OI&E was primarily due to foreign exchange fluctuations. OI&E will continue to be susceptible to market-related variations that could cause some level of volatility quarter-to-quarter.
Let me pivot to the capital return side of things. We allocated approximately $1 billion to open-market share repurchases, and we paid $261 million in dividends in the September quarter. I'd just highlight that in August we announced a 15% growth in the dividend in line with our plan to deliver an annual growth in the dividend. And I just mentioned, since paying our first dividend in 2014, we have now raised the dividend in 10 consecutive years. We have $9.8 billion remaining on our Board-authorized share repurchase plan. And we continue to track toward our long-term capital return plans of returning 75% to 100% of our free cash flow.
For the September quarter, diluted earnings per share was $0.86 above the midpoint of our guided range. The diluted share count was approximately 1.3 billion shares which was a reduction from the June quarter. On the balance sheet, our cash-and-cash equivalents totaled $6.1 billion at the end of the September quarter, up from $5.9 billion at the end of the June quarter. The increase was largely due to cash from operating activities, offset by cash allocated to share buyback, dividend payments, and capital expenditures.
Day sales outstanding was 64 days in the September quarter, an increase from 59 days that we saw in the June quarter. Inventory at the end-of-the September quarter totaled $4.2 billion. Inventory turns improved to 2.1 times from the prior quarter level of 1.9. We will continue to manage inventory levels to the best of our ability to align with customer demand. Our non-cash expenses for the September quarter included approximately $80 million for equity compensation, $80 million in depreciation, and $14 million in amortization. Capital expenditures for the September quarter were $11 million, up $10 million from the June quarter. Capital spending was mainly centered on lab investments in the United States and Asia, as well as manufacturing facilitization supporting our global strategy to be close to both customers' development, as well as manufacturing locations.
We ended the September quarter with approximately 17,700 regular full-time employees, which is an increase of approximately 500 people from the prior quarter. Headcount growth was predominantly in field and factory personnel, to support increased tool installation, as well as growing manufacturing activity levels.
Let's now turn to our non-GAAP guidance for the December 2024 quarter. We're expecting revenue of $4.3 billion, plus or minus $300 million. Gross margin of 47% plus or minus 1 percentage point. The gross margin guidance is reflective of a quarter-to-quarter headwind in customer mix. Operating margins of 30% plus or minus 1 percentage point. This reflects our continued commitment to managing our expense level as we prioritize critical R&D investment areas.
And finally, earnings per share of $0.87 plus or minus $0.10 based on a share count of approximately 1.29 billion shares. So let me wrap up. We continue to execute well in 2024. I believe that's reflected in our September results, as well as guidance for the December quarter. We're on track to achieve modest improvement in our operating leverage for the full calendar year, as we prioritize critical investments to extend our technology differentiation, while carefully managing overall spending levels.
The investments we're making position Lam well to benefit from the architectural and materials inflections we see ahead. We believe that we will continue to gain traction and outperform the overall growth in WFE in calendar year 2025. We continue to see 2025 as a growth year in both WFE and more importantly, Lam's top line.
Operator, that concludes our prepared remarks. We would now like to open up the call for questions.