US Patent 7998815 Shallow trench isolation

Shallow trench isolation methods are disclosed. In a particular embodiment, a method includes implanting oxygen under a bottom surface of a narrow trench of a silicon substrate and performing a high-temperature anneal of the silicon substrate to form a buried oxide layer. The method also includes performing an etch to deepen the narrow trench to reach the buried oxide layer. The method further includes depositing a filling material to form a top filling layer in the narrow trench.