In recent progress of semiconductor technology, minimum line width at pattern rule of 256MDRAM reticle, is 1.0 μm, the accuracy is ±0.05 μm, and repairing accuracy is required up to ± 10 μm. Moreover, it is necessary to repair small defect in fine pattern with 1~2 μm of L&S and composite defect such as contact hole defect with high-accuracy and high-stability, and to reduce splatter, rollup, and substrate damage. For improvement of laser processing quality, we have been developed new repairing technology to meet the above mentioned requirements, using laser diode pumped Q-switched pulse laser source with 1 mJ pulse energy, automatic high precision positioning system which is composed of two dimensional gray scale image processor in treating CCD camera image data of mask pattern, and new fine moving X-Y stages using hysteresis compensated piezo-actuator. The hysteresis is suppressed to less than O.2 μm for 30 μm moving distance, without drift. For these technology, we have realized the ± 0.10 μm repairing accuracy for an 5 μm square edge type defect. In this paper, we describe about laser mask repair technology for 256MDRAM reticle.