Patent ID: 8460998

Claim:
A method of fabricating a semiconductor device, comprising: forming a silicon nitride layer on a blocking insulating layer; forming a first tunnel insulating layer covering the silicon nitride layer, the forming of the first tunnel insulating layer including heat treating the silicon nitride layer, the first tunnel insulating layer including at least one of an oxide or a nitride-oxide; forming a second tunnel insulating layer, the second tunnel insulating layer including at least one of an oxide or a nitride-oxide; forming a third tunnel insulating layer; and forming an active layer covering the first tunnel insulating layer, wherein the second tunnel insulating layer is interposed between the first tunnel insulating layer and the active layer, and the third tunnel insulating layer is interposed between the second tunnel insulating layer and the active layer; wherein: the second tunnel insulating layer has a higher dielectric constant than the first tunnel insulating layer and the third tunnel insulating layer, and the first tunnel insulating layer has a different oxygen concentration or different nitrogen concentration from the second tunnel insulating layer.