SEMICONDUCTOR DEVICES INCLUDING TRENCH ISOLATION STRUCTURES AND METHODS OF FORMING THE SAME

Trench isolation methods include forming a first trench and a second trench in a semiconductor substrate. The second trench has a larger width than the first trench. A tower isolation layer is formed on the semiconductor substrate using a first high density plasma deposition process. The lower isolation layer has a first thickness on an upper sidewall of the first trench and a second thickness on an upper sidewall of the second trench. The second thickness is greater than the first thickness. An upper isolation layer is formed on the semiconductor substrate including the lower isolation layer using a second high density plasma deposition process, different from the first high density plasma deposition process. The second high density plasma deposition process includes an H<SUB>2 </SUB>treatment process.