Douglas R. Bettinger
Executive Vice President, and Chief Financial Officer at Lam Research
Thank you, Tim. Good afternoon, everyone, and thank you for joining our call today. We executed well in the June 2024 quarter. Our June quarter results came in above the midpoint or exceeded our guidance ranges for all financial metrics. We were pleased with the company's strong execution. For fiscal year 2024, we achieved the highest gross margin percentage since the merging of Lam with Novelis in 2013, coming in at 48.2% and we generated quite strong free cash flow of approximately $4.3 billion or 29% of revenue. Let's look at the details of our June quarter results.
Revenue came in at $3.87 billion, which was an increase from the prior quarter and over the midpoint of guidance. Our deferred revenue balance at the end of the quarter was -- or excuse me, $1.55 billion, which is a decrease of $194 million in the March quarter related to revenue recognized that was tied to customer advanced payments. As we sit here today, I believe deferred revenue remains stable at these levels for the foreseeable future. Let's turn to the revenue segment details.
June quarter systems revenue in memory was 36%, which was a decrease from the prior quarter level of 44%. The decline in the memory segment was mainly attributable to DRAM. DRAM came in at 19% of systems revenue compared with 23% in the March quarter as investments in mature nodes declined in the June quarter. DRAM revenue reached a new record in fiscal year 2024 with spending focused on DDR5 and HBM enablement as well as on the 1Y node. Nonvolatile memory came in at 17% of our systems revenue, which was down from the March quarter level of 21%. And just a reminder, we are characterizing one customer's investment in specialty DRAM as a non-ball investment since it has a nonvolatile component in the device. Net revenue was at a low point for this year, and I expect NAND investment to gradually improve as utilization rates return to more normal levels, our customers slowly increased spending in conversions to 2xx and 3xx layer devices into the next year.
The Foundry segment represented 43% of our systems revenue, which was roughly flat with the percentage concentration in the March quarter of 44%. Growth in shipments for data all around nodes was offset by a decline in mature node spending. The [Indecipherable] and other segment were 21% of system revenue in the June quarter, up from the prior level of 12%. The increase was driven by strength in mature node spending in China. With respect to the regional composition of our total revenue, the China region came in at 39%, down slightly from the prior quarter level of 42% and a little bit higher than our expectations from the previous earnings call. This was driven by domestic China spending. The next largest geographic concentration was Korea at 18% of revenue in the June quarter, versus 24% in the March quarter. Taiwan was 15% of revenue in the June quarter, which was an increase from 9% in the March quarter.
The customer support business group revenue in the June quarter pulled approximately $1.7 billion, an increase of 22% from the prior quarter level and 14% higher than the June quarter and calendar 2023. CSBG revenue represented 44% of our June quarter revenues and reached the highest point since the end of calendar 2022, driven primarily by an increase in Reliant systems, followed by growth in spares. Our Reliant Systems revenue benefited from strength in domestic China spending for specialty and mature nodes. Spares revenue increased largely due to continued improvement in utilization at our memory customers as well as a little bit of inventory stocking. I do not think CSBG will grow modestly in calendar year 2024.
Let's look at profitability. Our June quarter gross margin came in at 48.5% at the top end of our guided range and slightly down from 48.7% in the March quarter. June quarter gross margin benefited from continued improvement in factory efficiencies, which largely offset the headwind we saw in customer mix that we talked about on the last earnings call. Operating expenses for the June quarter were $689 million, down marginally from the prior quarter amount of $698 million. As Tim mentioned, we continue to prioritize spending in research and development to extend our technology differentiation as well as expand our product portfolio. I'd just point out that more than 70% of our total operating expenses were concentrated in research and development. The June quarter operating margin was 30.7%, above the guidance range mainly because of that strong gross margin performance. Our non-GAAP tax rate for the quarter was 11.5%. We estimate the tax rate for the remainder of the calendar year 2024 to be in the low to mid-teens level, and this rate will fluctuate from quarter-to-quarter.
Other income and expense for the June quarter was approximately $19 million in income compared with $10 million in income in the March quarter. The increase in OI&E was primarily the result of fluctuations in the fair value of our venture investments. And as we've talked about in the past, you will see variability in OI&E quarter-to-quarter. Let's look at the [Phonetic] capital return. We allocated approximately $382 million to share repurchases, and we paid $261 million in dividends in the June quarter. During the quarter, we announced that our Board of Directors approved a $10 billion share repurchase authorization. We have $10.8 billion remaining in the plan at the end of the June quarter. For fiscal year 2024, we returned $3.7 billion or 88% of free cash flow, which was in line with our long-term capital plans of returning 75% to 100% of free cash flow.
June quarter diluted earnings per share were $8.14, close to the high end of our guidance range. The diluted share count was 131 million shares on track with our expectations and down from the March quarter. Let's look at the balance sheet. Cash and cash equivalents totaled $5.9 billion at the end of the June quarter, up a little bit from $5.7 billion at the end of the March quarter. The sales outstanding were 59 days in the June quarter, a slight increase from 57 days in the March quarter. June quarter inventory turns of 1.9 times compared with 1.8 times in the prior quarter. We are making progress in bringing inventory levels down, and we'll continue to work on this throughout the rest of calendar year 2024.
Our noncash expenses for the June quarter included approximately $79 million for equity compensation, $74 million in depreciation and $14 million in amortization. Capital expenditures were $101 million, flat with the March quarter level was spending mainly centered on lab investments in the United States and Asia as well as manufacturing facilities in Asia, supporting our global strategy to be close to our customers' development and manufacturing locations. We ended the June quarter with approximately 17,200 regular full-time employees, which was flat with the prior quarter. Let's turn to our non-GAAP guidance for the September 2024 quarter. We're expecting revenue of $4.05 billion, plus or minus $300 million. Gross margin of 47%, plus or minus 1 percentage point. This gross margin decline is reflective primarily of an unfavorable quarter-to-quarter change in customer mix. I expect this change to continue to be a slight incremental headwind in the December quarter.
Operating margins of 29.5%, plus or minus 1 percentage point. Gross margin and operating margin included impact from ongoing transformation costs related to projects to improve our systems and operations. As we communicated at the beginning of the year, we're focused on reengineering our business processes and systems to drive operational efficiencies and to implement AI at greater scale. And finally, we're forecasting earnings per share of $8 plus or minus $0.75 based on a share count of approximately 131 million shares.
Let me wrap up. As we finish the first half of calendar year 2024, I was pleased that we were able to execute to the objectives we shared at the beginning of the year. We prioritize investment to extend our technology differentiation while driving operational improvements. We're encouraged that the spares business recovery is beginning and upgrade activity should improve as we exit the calendar year.
Longer term, Lam is well positioned to capitalize the increase in etch and deposition intensity by delivering new capabilities and multiple new manufacturing inflections that we see ahead. We look forward to talking to you in February at our planned Investor Day about the long-term opportunities for Lam to continue our outperformance in the semiconductor industry.
Operator that concludes our prepared remarks. Tim and I would now like to open up the call for questions.