A semiconductor memory device includes a substrate having first and second source/drain regions therein and a channel region therebetween. The device also includes first and second charge storage layers on the channel region, a first insulating layer on the channel region between the first and second charge storage layers, and a gate electrode on the insulating layer opposite the channel region and between inner sidewalls of the first and second charge storage layers. The gate electrode extends away from the substrate beyond the first and second charge storage layers. The device further includes second and third insulating layers extending from adjacent the inner sidewalls of the first and second charge storage layers along portions of the gate electrode beyond the first and second charge storage layers. Related methods of fabrication are also discussed.