| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacturing method, which comprises a trench isolation structure suitable for turning into minute size. SOLUTION: An upper end part C of a semiconductor substrate 1, which is opened by a trench 4 is rounded in a thermal oxidizing processing. Then, a silicon nitride film is etched in horizontal direction with a thermal phosphoric acid to expose the upper end part C, and then the trench 4 and the upper end part C are filled with an insulating material 6a (figure 3 (a)). An insulating material 6a is etched to planarize a silicon nitride film 3c and the insulating material 6b (figure 3 (b)). The silicon nitride film 3c is selectively removed using thermal phosphoric acid (figure 3 (c)). Then the insulating material 6b is etched so that its upper surface is almost level with the upper end part C of the semiconductor substrate 1, to form an insulating material 6 (figure 3 (d)).
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