| abstract |
Formed on a substrate are an inorganic interlayer film, an organic interlayer film, a lower mask made of silicon oxide and an upper mask made of silicon nitride in this order. An opening is formed in the upper mask. Then, a cover mask made of silicon oxynitride and having a film thickness of 20 to 100 nm is formed on the upper mask. Thereafter, an Anti-Reflection Coating film and a resist film are formed thereon. Subsequently, the Anti-Reflection Coating film, the cover mask and the lower mask is etched using the resist film as a mask. Then, the organic interlayer film and the inorganic interlayer film are etched using the cover mask as a mask to form a via hole. Simultaneously, the cover mask is removed to make the upper mask exposed. Thereafter, the organic interlayer film is etched using the upper mask as a mask to form an interconnect trench. |