Semiconductor devices including trench isolation structures and methods of forming the same

A trench isolation method, comprising:

• forming a first trench and a second trench in a semiconductor substrate, the second trench having a larger width than the first trench;
• and
• forming an isolation layer on the semiconductor substrate using a high density plasma deposition process, wherein the high density plasma deposition process comprises:
• positioning the semiconductor substrate including the first and second trenches on a substrate support within a high density plasma chemical vapor deposition (HDPCVD) reactor;
• performing a low temperature HDP deposition process on the semiconductor substrate, including injecting a silicon source gas into the HDPCVD reactor;
• performing an etch on the semiconductor substrate, including injecting an etch gas into the HDPCVD reactor;
• performing an H2 treatment process on the semiconductor substrate, including injecting H2 into the HDPCVD reactor;
• and performing an O2 treatment on the semiconductor substrate, including injecting O2 into the HDPCVD reactor.