A semiconductor device with an L-shape spacer and the method for manufacturing the same are provided. The semiconductor device comprises a substrate, a composite spacer, and a tunnel insulating layer. The substrate comprises a shallow trench isolation structure and a neighboring active area. The composite spacer is formed on the sidewall of the shallow trench isolation structure, and further comprises a first insulating layer and an L-shape second insulating layer spacer, wherein the first insulating layer is located between the L-shape second insulating layer spacer and the substrate. The tunnel insulating layer is located on the substrate of the active area and connects to the first insulating layer of the composite spacer on its corresponding side.