A method of decreasing fin bending, includes providing a substrate including a plurality of fins, wherein a plurality of trenches are defined by the fins, the trenches include a first trench and a second trench, and the second trench is wider than the first trench. Later, a flowable chemical vapor deposition process is performed to form a silicon oxide layer covering the fins, filling up the first trench and partially filling in the second trench. After that, the silicon oxide layer is solidified by a UV curing process. Finally, after the UV curing process, the silicon oxide layer is densified by a steam anneal process.