Layout design system, system and method for fabricating mask pattern using the design system

Provided are a layout design system, and a system and a method to fabricate a mask pattern using the same. The layout design system comprises: a processor; a stitch module; and a storage unit which stores layout design, which is placed in accordance with a predetermined design rule and includes: a first pattern group including a first pattern which is patterned in a first time; and a second pattern group including a second pattern which is patterned in a second time, which is different from the first time. The stitch module detects an iso-pattern among the second pattern by using the processor, and designates one or more of the first pattern distanced from the iso-pattern for a predetermined distance or farther into the second pattern group by using the processor. The present invention aims to provide a layout design system and a system and a method to fabricate a mask pattern, which can reduce defects in patterning due to differences in interval or density of patterns.