Method of fabricating semiconductor device

A method of fabricating a semiconductor device, comprising:

• providing a substrate;
• sequentially forming a first mask layer and a second mask layer on the substrate;
• performing a self-aligned double patterning process to form a plurality of mask patterns parallel extended along a first direction on the second mask layer, and forming a spacer on the second mask layer;
• forming a photoresist layer on the second mask layer, the photoresist layer overlapping with two opposite ends of each of the mask patterns;
• performing an etching process through the photoresist layer and the mask patterns, to form a plurality of first patterns, a plurality of second patterns, and a plurality of third patterns, the first patterns parallel extending along the first direction, the second patterns extending along a second direction, the third patterns extending along a third direction, and each of the first patterns directly contacting the second patterns or the third patterns;
• and
• forming an active structure and a shallow trench isolation in the substrate, the active structure comprising:
• a first active area, comprising a plurality of active area units being parallel extended along the first direction;
• and
• a second active area, disposed outside the first active area,
• the second active area the second active area comprising a first edge extending along the second direction and a second edge extending along the third direction, and the first edge directly connected to the second edge, wherein the second direction intersects and is not perpendicular to the first direction, and the second direction is perpendicular to the third direction.