Shallow trench isolation structure and method for forming the same

摘要

The invention provides a STI structure and method for forming the same. The STI structure includes a semiconductor substrate; a first trench embedded in the semiconductor substrate and filled up with a first dielectric layer; and a second trench formed on a top surface of the semiconductor substrate and interconnected with the first trench, wherein the second trench is filled up with a second dielectric layer, a top surface of the second dielectric layer is flushed with that of the semiconductor substrate, and the second trench has a width smaller than that of the first trench. The invention reduces dimension of divots and improves performance of the semiconductor device.