Patent ID: 8367554

Claim:
A method for forming a shallow trench isolation region, comprising the following steps: forming a patterned passivation layer on a silicon substrate; etching a portion of the silicon substrate to a certain depth by using the patterned passivation layer as a mask, wherein convex and concave shaped portions are formed on the surface of the etched silicon substrate; performing an isotropic plasma etching process on the etched silicon substrate with mixed gases containing oxygen and a fluorine-based gas; cleaning the silicon substrate subjected to the isotropic plasma etching process, thereby forming a shallow trench; and filling the shallow trench to form a shallow trench isolation region, wherein the isotropic plasma etching process is performed using an inductive coupled plasma process with a zero bias power, in which no electrical field and no orientation movement of the plasma are generated at the surface of the etched silicon substrate, wherein height differences between the top of the convex portions and the bottom of the concave portions are reduced.