Abstract: Two trenches are formed at a predetermined distance on a main surface of a semiconductor substrate. An oxide film and a nitride film are successively formed on the main surface of the semiconductor including the inner surfaces of the trenches. After a resist is formed over the whole surface including the inner surfaces of the trenches, the resist is patterned to expose a portion of the nitride film on a side surface of each trench. The exposed portions of the nitride film are removed by using the patterned resist as a mask and thermal oxidation is applied. Then, an isolation oxide film is formed on a region between the trenches and an end of a bird's beak is located on a side surface of each trench and is connected to the oxide film formed in each trench.

Abstract: A multilayer interconnection is prepared by forming a stable insulating film on a nitride film which is formed on a first interconnection metal layer, and then, a second interconnection metal layer is formed on the insulating film. The insulating film can be made of aluminum oxide, an oxynitride or the other metal oxide. A silicon rich layer can be used for this purpose.