Method for forming a shallow trench isolation structure with reduced encroachment of active regions and a semiconductor structure therefrom

Abstract

A method for forming a shallow trench isolation (STI) structure using two individual STI trench etching processes is provided. A first STI etching process forms first trenches with one or more sizes in rows along a first dimension in a silicon substrate. A first dielectric is filled in the first trenches following a first thermal oxidation forming a first liner oxide surrounding the first trenches. A second STI trench etching process forms second trenches with one or more sizes in a second dimension to define active regions separated from each other by the first trenches filled with the first dielectric material and second trenches. A second dielectric is filled in the second trenches following a second thermal oxidation forming a second liner oxide surrounding the second trenches. Active region encroachment caused by the first and second thermal oxidation is reduced by doing the two individual STI trench etching processes.

What is claimed is: 
     
         1 . A semiconductor structure, comprising:
 a silicon substrate;   a plurality of first trenches with one or more sizes filled with a first dielectric material formed in the silicon substrate along a first dimension;   a plurality of second trenches with one or more sizes filled with a second dielectric material formed in the silicon substrate along a second dimension; and   a plurality of active regions with one or more sizes formed in the silicon substrate, wherein each of the active regions is rectangular-shaped with round corners and separated from each other by the first trenches filled with the first dielectric material and the second trenches filled with the second dielectric material.   
     
     
         2 . The semiconductor structure of  claim 1 , wherein the first trench has a different size from that of the second trench. 
     
     
         3 . The semiconductor structure of  claim 1 , where the first trenches are interdigitated with the second trenches.