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 on what I know is a very busy earnings season. As the world continues to face challenges with the pandemic, I hope you and your families have been safe and healthy since we last spoke with you. Lam continued to deliver outstanding performance with record quarterly revenue, operating income and earnings per share in the June 2021 quarter. Our revenue, gross margin and operating income came in at or above the midpoint of our guidance, and earnings per share were above our guidance range. We're extremely pleased with our operational execution, and we thank all of our customers, suppliers and employees for their dedication and support. Our revenue for the June quarter was $4.15 billion, representing an increase of 8% from the March quarter.
We had record revenue in both our systems and our Customer Support Business Group. So let me now turn to the details on systems revenue. The Memory segment continues to be an area of strength for Lam and represented 59% of systems revenue in the June quarter. The NAND segment concentration was essentially flat with the prior quarter at 49% of our systems revenue and again hit another record level in terms of revenue dollars. We saw customer investments in both capacity adds and conversions with spending primarily on 128-layer class devices. In the DRAM segment, we had 10% of our June quarter systems revenue versus 14% in the prior quarter. The DRAM investments were concentrated mainly in the one z and one alpha nodes. And I would just mention, we do see DRAM spending strengthening into the second half of this year. For the Foundry segment, we had our second consecutive quarter of record revenues, coming in at 35% of our June systems revenue as compared with 31% in the March quarter.
Foundry spending is occurring in both leading-edge and mature technologies to meet the end demand for various market drivers like AI, 5G and gaming as well as specialty chips needed for things like IoT, image sensors and power devices. And finally, Logic and Other contributed the remaining 6% of systems revenue in the June quarter, which was essentially flat to the prior quarter percentage. Now looking at the regional profile of our total revenue. The China region came in at 37% of our total revenues, up from 32% in the March quarter. The spending profile for the China region was generally balanced between the domestic and multinational customers with their fabs that are located in China. The Korea region also contributed -- or continued to be very strong in the June quarter, representing 30% of revenues. CSBG, which is our installed base business, came in at nearly $1.4 billion, which, as I noted, is another high point for this group.
The revenue level is an increase of 6% from the March quarter and 49% higher than the same quarter in 2020. All of the subsegments of this business are delivering excellent performance: the Reliant product line that serves specialty market upgrades where we're extending the life of our customers' tools as well as spares and service that are supporting the high industry utilizations. All subsegments strongly contributed in the quarter. So let me shift to profitability. June quarter gross margin was 46.5%, right at the midpoint of the guided range. I'll remind you that our gross margins fluctuate quarter-to-quarter due to overall business levels, along with customer and product mix. I would mention there continues to be elevated air freight and logistics costs due to the COVID environment impacting us in the current quarter, which are also reflected in the September quarter guidance.
Operating expenses for June were $574 million, slightly higher than the prior quarter. You may note in our earnings release that we did incur a charge during the quarter of approximately $6 million related to an asset impairment of the product line that we're shutting down. This charge was excluded from our non-GAAP operating expenses. We've demonstrated our ability to scale the company profitably as we've continued to decrease operating expenses as a percent of revenue. I'll also note that we've continued to prioritize R&D spending to ensure that we have the resources to continue to build on our technically differentiated leadership positions, and we maintained an emphasis on R&D spending, and it continues to represent approximately 2/3 of our operating expenses. June quarter operating margin showed solid performance, coming in over the midpoint of our guidance range at 32.6%, reflecting strong gross margin and operating expense management.
This operating income percentage represents an all-time high-water mark for Lam Research. Our non-GAAP tax rate for the quarter was 12.6%, generally in line with our expectations. And as I've noted in prior calls, our tax rate will fluctuate from quarter-to-quarter. We expect the ongoing tax rate to be in the low teens level for the 2021 calendar year. And I would just mention we're continuing to monitor potential tax changes that are under discussion in the current United States administration. Other income and expense was approximately $23 million in expense, which is lower than the prior quarter as a result of a $30 million market gain in one of our venture capital investments. As we previously noted, OI&E is subject to market-related volatility that could cause a difference from any typical run rate. And also, just to remind you, beginning in the March quarter of 2020, the benefits and costs of our employee deferred compensation plan are no longer mismatched in our non-GAAP results.
This mismatch was $17 million for the June 2021 quarter. And if you're interested, you can see the details in the GAAP reconciliation tables in the earnings release. So now let me shift to capital return. We paid $185 million in dividends and allocated $440 million towards share buyback. This is in line with our long-term capital return plans of 75% to 100% of our free cash flow. Earnings per share came in at $8.09, above the guidance range. The outperformance is due to the higher revenue and expense management as well as the favorability I noted in OI&E. The diluted share count balance was down slightly from the March quarter level, coming in at 144 million shares. During the June quarter, we redeemed the remaining 2041 convertible notes, which I'm happy to tell you is the last convert that was in our capital structure. Let me shift to the balance sheet. Cash and short-term investments, including restricted cash, totaled $6 billion, which is flat with the prior quarter.
We had record performance in the June quarter for cash flows from operations, which came in at $1.4 billion. During the quarter, our cash generation was deployed to the paydown of $800 million of senior notes that were due in June as well as cash outlays for the capital return activities that I mentioned. Days sales outstanding was flat to the March quarter at 66 days. Inventory turns were up slightly from the prior quarter level, coming in at 3.3 times. June quarter noncash expenses included approximately $56 million for equity compensation, $60 million for depreciation and $18 million for amortization. We are investing in increasing our capacity and support of customers. And as a result, capital expenditures for the June quarter were up from the March level and came in at $105 million. We have investments occurring around the globe with our new Malaysia factory, which is formally opening this quarter, expansion in our U.S. critical spare parts facility in Ohio and R&D investments in our new Korean lab facility. We expect to see somewhat levels -- somewhat elevated levels, excuse me, of capital expenditures in the remainder of calendar year 2021 as we support these growth initiatives.
The head count level ending the June quarter was approximately 14,100 regular full-time employees. Resources have been added in our factories and in the field to meet the increased output levels and to support customers in their technology evaluations as well as tool installation requirements. My final commentary to touch on for the June quarter is a follow-up in the ESG space, which obviously is strategically important for Lam Research. In June, we extended and upsized our revolving credit facility to $1.5 billion. We transitioned this facility to a sustainability-linked revolver, which includes a pricing structure that is linked to certain performance metrics for energy savings and employee safety. In addition to the ESG focus areas that Tim noted, this credit facility is further demonstration of our commitment to integrate ESG principles into all aspects of how we operate as a company. So now looking ahead, I'd like to provide our non-GAAP guidance for the September 2021 quarter.
We're expecting revenue of $4.3 billion, plus or minus $250 million; gross margin of 46%, plus or minus one percentage point; operating margins of 32%, plus or minus one percentage point; and finally, earnings per share of $8.10, plus or minus $0.50, based on a share count of approximately 143 million shares. We continue to maintain a widened revenue range as we work to mitigate ongoing output challenges in our global supply chain. These supply chain challenges are also driving a modest headwind in our guided gross margin. Customer demand continues to look strong in the second half of 2021 as well as into next year. Lam is operating at record levels of financial performance as a result of the tireless efforts of our operational organizations and supply chain partners. We continue to progress on our longer-term share gain objectives with investments in new platforms like Sense.i and dry resist. We'd like to thank the company for rising to the challenge and delivering on these objectives. Operator, that concludes my prepared remarks.
Tim and I would now like to open up the call for questions.