Patent ID: 6323105
Filing Date: 2001-11-27
Classification: H01L

Abstract:
A method for fabricating an improved shallow trench isolation (STI) structure by combining uses of a STI process and a local oxidation (LOCOS) process, the method comprising:forming a hard material layer on a semiconductor substrate;patterning the hard material layer to form an opening, which exposes a region of the substrate, wherein the improved STI structure is to be found in the exposed region in the substrate;forming a first liner oxide layer over the substrate so that the first liner oxide layer is conformal to a substrate surface;forming a hard spacer on each sidewall of the opening of the hard material layer, wherein a portion of the first liner oxide layer at a bottom surface of the opening is still exposed;forming a first field oxide (FOX) layer on the exposed portion of the first liner oxide layer;removing the hard spacer;forming a trench in the substrate, using the hard material layer and the FOX layer as a mask, so that the trench is formed at each side of the FOX layer within a region of the opening of the hard material layer.forming a second liner oxide layer over an inner surface of the trench;filling the trench with a polysilicon layer,etching back the polysilicon layer to expose a top surface of the first field oxide layer;forming a second FOX layer over the polysilicon layer to merge the second liner oxide layer and the first FOX layer so that the polysilicon layer is fully isolated from the substrate; andremoving the hard material layer to expose the substrate.