| 摘要 |
PROBLEM TO BE SOLVED: To obtain a method for fabricating a semiconductor device having good characteristics where junction leak current is low and no parasitic transistor is generated in the isolation trench. SOLUTION: The method for fabricating a semiconductor device isolated by an isolation trench comprises first etching step for forming a first trench 20 wider than the trench pattern of a silicon nitride film 16 and shallower than a groove for forming the isolation trench in the upper layer of a silicon substrate 12 by etching the silicon substrate by an isotropic etching method using the silicon nitride film as a mask when the isolation trench is made in the silicon substrate, second etching step for forming an isolation trench comprising first and second trenches by etching the bottom of the first trench 20 using the silicon nitride film as a mask and forming a second trench 22 having opening of same width as the bottom of the first trench continuously in the bottom of the first trench, and a step for thermally oxidizing the groove for forming the isolation trench to form a thermal oxidation film on the wall of the trench and then shaping the wall of the trench.
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