What was the company's gross margin in Q1 2020? 
 to semiconductor demand at some point this year. It's a fluid situation, and it is hard to predict exactly when this will happen. But with that in mind, forecasting beyond Q2 is challenging.
Consequently, due to the evolving and uncertain impact of COVID-19 will have on the semiconductor industry, we are withdrawing the 2020 sales and EPS annual guidance, we gave in February. While it's unclear how the market will perform for all of 2020, the two other positive growth drivers, totaling 400 to 600 basis points of growth are still in place for us in 2020. The first one, as you remember, is the key technology node transitions to logic and memory we expected for 2020. And these are still on track, which means we continue to expect to outperform the market by approximately 200 to 300 basis points in 2020, driven by an increase in our served market and market shares as a result of a number of large customers transitioning to new technology nodes, both in logic and memory.
The second is that we continue to expect that as the acquisition we have already made will add approximately 200 to 300 basis points to our growth in 2020. Clearly, we are in unprecedented times, and we will be facing a high level of uncertainty for the balance of the year. But we feel very optimistic about the long-term fundamentals of the industry. And we feel confident in the things we can control, including our competitive and financial position.
First, we believe that the secular semiconductor demand will continue to be very attractive. Our society will continue to need more and better chips. And in a strange way, COVID-19 could lead to an acceleration of the digitalization and automation of the economy, which will be favorable for the semiconductor industry. Second, we have confidence in our competitive position.
And to further secure this position, we will maintain significant R&D and capital investment levels in 2020 despite the prevailing short-term uncertainty. These investments are essential to a number of critical joint development initiatives with several key customers. As you know, greater materials intensity and greater materials purity will be the primary defining factors of the next-generation of semiconductor performance, and we want to be in a position to capitalize on the many new opportunities in front of us. Finally, we feel very confident that our experience, disciplined execution and strong balance sheet will allow us to navigate this period of uncertainty, while continuing to invest in the future.
Our team has very effectively managed challenging times in the past, and we will take the necessary steps to align our business to market conditions, as they evolve. Before turning over to Greg, I want to take a minute to thank the Entegris teams and our partners around the world for their dedication and their relentless efforts during this challenging period. And I also want to thank our customers for the trust they place in Entegris. Now let me turn the call to Greg.
Greg?
Greg Graves -- Chief Financial Officer
Thank you, Bertrand. In my section today, I'm going to cover our first-quarter financial performance and our second-quarter guidance. I'm also going to discuss how our liquidity and balance sheet strength provides a significant flexibility. As Bertrand said, in spite of all the challenges brought on by the COVID-19 crisis, the first quarter was solid for Entegris.
Q1 sales of $412 million were slightly below the low end of our guidance and were up 5% year over year and down 3% sequentially. As Bertrand said, the negative impact of the coronavirus to our supply chain is not material. Q1 GAAP diluted EPS was $0.45 per share, up 88% year over year and up 7% sequentially. And non-GAAP EPS of $0.55 was at the high end of our guidance range, up 10% year over year and flat sequentially.
Moving on to gross margin, GAAP and non-GAAP gross margin was approximately 45% in Q1. Gross margin was a bit below our original expectations, driven primarily by the modest manufacturing interruptions related to COVID-19 and lower-than-expected volume. We
 to semiconductor demand at some point this year. It's a fluid situation, and it is hard to predict exactly when this will happen. But with that in mind, forecasting beyond Q2 is challenging.
Consequently, due to the evolving and uncertain impact of COVID-19 will have on the semiconductor industry, we are withdrawing the 2020 sales and EPS annual guidance, we gave in February. While it's unclear how the market will perform for all of 2020, the two other positive growth drivers, totaling 400 to 600 basis points of growth are still in place for us in 2020. The first one, as you remember, is the key technology node transitions to logic and memory we expected for 2020. And these are still on track, which means we continue to expect to outperform the market by approximately 200 to 300 basis points in 2020, driven by an increase in our served market and market shares as a result of a number of large customers transitioning to new technology nodes, both in logic and memory.
The second is that we continue to expect that as the acquisition we have already made will add approximately 200 to 300 basis points to our growth in 2020. Clearly, we are in unprecedented times, and we will be facing a high level of uncertainty for the balance of the year. But we feel very optimistic about the long-term fundamentals of the industry. And we feel confident in the things we can control, including our competitive and financial position.
First, we believe that the secular semiconductor demand will continue to be very attractive. Our society will continue to need more and better chips. And in a strange way, COVID-19 could lead to an acceleration of the digitalization and automation of the economy, which will be favorable for the semiconductor industry. Second, we have confidence in our competitive position.
And to further secure this position, we will maintain significant R&D and capital investment levels in 2020 despite the prevailing short-term uncertainty. These investments are essential to a number of critical joint development initiatives with several key customers. As you know, greater materials intensity and greater materials purity will be the primary defining factors of the next-generation of semiconductor performance, and we want to be in a position to capitalize on the many new opportunities in front of us. Finally, we feel very confident that our experience, disciplined execution and strong balance sheet will allow us to navigate this period of uncertainty, while continuing to invest in the future.
 Our team has very effectively managed challenging times in the past, and we will take the necessary steps to align our business to market conditions, as they evolve. Before turning over to Greg, I want to take a minute to thank the Entegris teams and our partners around the world for their dedication and their relentless efforts during this challenging period. And I also want to thank our customers for the trust they place in Entegris. Now let me turn the call to Greg.
Greg?
Greg Graves -- Chief Financial Officer
Thank you, Bertrand. In my section today, I'm going to cover our first-quarter financial performance and our second-quarter guidance. I'm also going to discuss how our liquidity and balance sheet strength provides a significant flexibility. As Bertrand said, in spite of all the challenges brought on by the COVID-19 crisis, the first quarter was solid for Entegris.
Q1 sales of $412 million were slightly below the low end of our guidance and were up 5% year over year and down 3% sequentially. As Bertrand said, the negative impact of the coronavirus to our supply chain is not material. Q1 GAAP diluted EPS was $0.45 per share, up 88% year over year and up 7% sequentially. And non-GAAP EPS of $0.55 was at the high end of our guidance range, up 10% year over year and flat sequentially.
Moving on to gross margin, GAAP and non-GAAP gross margin was approximately 45% in Q1. Gross margin was a bit below our original expectations, driven primarily by the modest manufacturing interruptions related to COVID-19 and lower-than-expected volume. We