| 摘要 |
PROBLEM TO BE SOLVED: To prevent adverse effect on transistor characteristics by etching an insulating film slightly remaining in an isolation region along with a semiconductor substrate using an unetched insulation film as a mask thereby eliminating deterioration of film quality due to residual organic components. SOLUTION: A thermal oxide film 102 and a silicon nitride film 103 are formed on a silicon substrate 101. An opening is then made in resist 104 in an isolation region where the silicon nitride film 103 and the thermal oxide film 102 are subjected to selective etching. Subsequently, the resist 104 is peeled and etching is performed using the silicon nitride film 103 as a mask and a deep trench 106 is made in the remaining the thermal oxide film 105 and the silicon substrate 101. Thereafter, a thermal oxide film 107 is formed on the surface of the silicon substrate. Since a photoresist film is not used as a mask at the time of etching the deep trench 106, a high quality uniform thermal oxide film 107 having reduced contaminant component is formed.
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