A spinal fusion device having a spacer and a fastener and an associated method of use are disclosed. The spinal fusion device preferably has features to prevent excessive insertion of the spacer between two adjacent vertebra； to ensure proper fenestration, to ensure tight engagement between the spacer and the fastener and between the spinal fusion device and two adjacent vertebrae, to hinder back-out of screws used by the fastener, and to promote compaction and displacement of bone graft material to enhance the fusion process.
