Method for grouping region of interest of mask pattern and measuring critical dimension of mask pattern using the same

A method of fabricating a mask used in manufacturing a semiconductor device, comprising:

• measuring a critical dimension of a mask pattern, including:
• finding a candidate region of interest having a first critical dimension in a field of view (FOV) of a measuring device,
• determining a candidate group region of interest including a mask design before optical proximity correction of the mask pattern, and
• finding a target group region of interest including a target region of interest by excluding candidate regions of interest having lengths beyond a predetermined region of interest length range;
• altering a layout of the mask pattern according to the critical dimension of the mask pattern to provide an altered layout;
• and
• fabricating the mask according to the altered layout.