Method of fabricating semiconductor device

A method of fabricating a semiconductor device, comprising:

• sequentially forming a lower layer and an upper layer on a substrate;
• forming, on the upper layer, a first set of sacrificial patterns at a first region of the substrate and a second set of sacrificial patterns at a second region of the substrate;
• forming first spacers on opposite sidewalls of each sacrificial pattern of the first set of sacrificial patterns and second spacers on opposite sidewalls of each sacrificial pattern of the second set of sacrificial patterns;
• selectively removing the first set of sacrificial patterns and the second set of sacrificial patterns without removing the first or second spacers, thereby exposing part of the upper layer;
• etching the upper layer exposed by the first and second spacers to form a first set of upper patterns and a second set of upper patterns under the respective first spacers and second spacers;
• removing the first spacers and second spacers to expose top surfaces of the first and second sets of upper patterns;
• forming third spacers on opposite sidewalls of each upper pattern of the first set of upper patterns, wherein each pattern of the first set of upper patterns has a first width, and each pattern of the second set of upper patterns and its corresponding third spacers has a second width greater than the first width;
• and
• etching the lower layer using the first set of upper patterns, and the second set of upper patterns and corresponding third spacers to form first fins of the first region on the substrate, the first fins having the first width, and to form second fins of the second region on the substrate, the second fins having the second width.