On the call today are Gideon Argov, President and CEO; Bertrand Loy, Chief Operating Officer; and Greg Graves, Chief Financial Officer.
Before turning the call to Gideon, I do want to let everyone know that Entegris will be holding an Analyst Day on May 23 in New York City. You can contact me for more information about that event.
And with that, Gideon will now begin the call.
Thank you, Steve, and good morning, and thank you for joining the call. We had a strong start to the year and have a number of reasons to be pleased with our performance in the first quarter. We achieved sales growth of 7% for the fourth quarter of 2011 and continue to see strong demand for our products used to support leading-edge processes. We executed well, and achieved solid financial results, improved our adjusted operating margins to 16.7% and recorded cash earnings per share of $0.14. And in addition, we made investments to extend our technological leadership for years to come. I have more to say about this in a moment.
Looking at our revenue trends in the quarter. We continue to benefit from technology-driven spending by leading semiconductor device makers and ramping production of 28-nanometer fabs. We believe utilization rate of 2X nodes for many of our key fab customers with 90% to 100%. While on legacy side of the industry, utilization rates range between 50% and 70%. Overall, utilization wafer starts in the industry appear to be down in the quarter, according to most industry analysts.
We clearly benefit from the industry's adoption of advanced processes and we've seen broad-based demand increase in the quarter for a number of filtration and fluid handling products for wet etch and clean application and for our advance FOUPs for wafer handling. These products have proven themselves to be essential to address the yield issues typically come with implementing new and highly complex processes. Although we're addressing this advanced contamination control needs with both unit driven and capital driven products, our mix of sales of 65% unit driven and 35% capital driven did shift slightly to the unit side.