Abstract: A method of fabricating an STI trench includes providing a substrate. Later, a first mask is formed to cover the substrate. The first mask includes numerous sub-masks. A first trench is disposed between each sub-mask. Subsequently, a protective layer is formed to fill up the first trench. Then, a second mask is formed to cover the first mask. The second mask includes an opening. The sub-mask directly disposed under the opening is defined as a joint STI pattern. After that, the joint STI pattern is removed to transform the first mask into a third mask. Later, the second mask is removed followed by removing the protective layer. Finally, part of the substrate is removed by taking the third mask as a mask to form numerous STI trenches.

Abstract: A method of fabricating an isolation structure is provided. A first oxide layer and a first, second, and third hard mask layers are formed on a substrate. A patterned third hard mask layer is formed. Second oxide layers are formed on sidewalls of the patterned third hard mask layer and a fourth hard mask layer is formed between the second oxide layers. The second oxide layers and the second hard mask layer are removed using the patterned third hard mask layer and the fourth hard mask layer as a mask, to form a patterned second hard mask layer. The patterned third hard mask layer and the fourth hard mask layer are removed. A portion of the patterned second hard mask layer is removed to form trench patterns. A patterned first hard mask layer and first oxide layer, and trenches located in the substrate are defined. An isolation material is formed.