Method for fabricating patterned structure of semiconductor device

A method for fabricating a patterned structure of a semiconductor device, comprising:

• forming a plurality of first mandrels and a plurality of second mandrels on a substrate, wherein a first spacing is defined between the two adjacent first mandrels and a second spacing is defined between the two adjacent second mandrels, the first spacing being wider than the second spacing, and the widths of the first mandrels are equal to the widths of the second mandrels;
• forming a cover layer to cover the first mandrels while exposing the second mandrels;
• etching the exposed second mandrels;
• removing the cover layer;
• concurrently forming a plurality of first spacers on the sides of the first mandrels and a plurality of second spacers on the sides of the second mandrels after removing the cover layer;
• and
• transferring a layout of the first and second spacers to the substrate, so as to form a plurality of fin-shaped structures.