Fish & Richardson P.C.
Trench isolation process
 A method of providing isolation structure in a semiconductor device having a shallow trench with a rounded top corner is provided for preventing stress centralization as well as current leakage of a device. The method includes the steps of: (a) sequentially forming a pad oxide layer and a silicon nitride layer on a semiconductor substrate; (b) forming an opening in the silicon nitride layer by a first anisotropic etching process, so as to expose an area for forming a shallow trench; (c) performing a wet etching process to remove the pad oxide layer within the opening, the wet etching process removing a portion of the pad oxide layer extending from the opening and under the silicon nitride layer; (d) performing an isotropic etching process to form a hollow with a rounded top corner in the semiconductor substrate, wherein the rounded top corner is located under the silicon nitride layer; and (e) continuously etching the hollow by a second anisotropic etching process using the silicon nitride layer as a mask, thereby forming a shallow trench having a rounded top corner in the semiconductor substrate. 
Winbond Electronics Corp.
Y H
Y10S H01L
additional inventional
Michael
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