Nonvolatile semiconductor memory device and manufacturing method thereof

Abstract

In accordance with an embodiment, a nonvolatile semiconductor memory device includes a substrate including a semiconductor layer including an active region, a first insulating film on the active region, a charge storage layer on the first insulating film, an element isolation insulating film defining the active region, a second insulating film, and a control electrode on the second insulating film. The top surface of the element isolation insulating film is placed at a height between the top surface and the bottom surface of the charge storage layer, thereby forming a step constituted of the charge storage layer and the element isolation insulating film. The second insulating film covers the step and the charge storage layer. The second insulating film includes a first silicon oxide film and a first silicon nitride film on the first silicon oxide film. Nitrogen concentration in the first silicon nitride film is non-uniform.

Dependencies are inferred from the claim text.