| 摘要 |
PURPOSE: A method for forming a trench in a semiconductor device is provided to form a conductive film and an element isolation film with uniform heights by preventing the loss of the conductive film. CONSTITUTION: A tunnel insulating film(104), a first hard mask, a conductive film, and a second hard mask are formed on a semiconductor substrate. The second hard mask film and the first hard mask film are etched. A spacer(118a) is formed on the sidewall of the first and the second hard masks. A conductive film between the first hard mask and the second hard mask are etched. A buffer film(120) is formed using a material with different etching selectivity from that of the conductive film. A trench is formed by etching the tunnel insulating film and the semiconductor substrate.
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