X-ray mask pattern accuracy was improved by a new method that superimposes multiple exposures using different field sizes. Significant errors induced by frame mounting were completely suppressed by a new one-point mounting method. Highly accurate Ta absorber patterns were obtained by ECR dry etching using a gaseous mixture of Cl2, O2, and Ar. X-ray masks with pattern placement accuracies as high as 0.056 μm (3σ) were successfully fabricated.