Methods of forming a resistive memory device include forming an insulation layer on a semiconductor substrate including a conductive pattern, forming a contact hole in the insulation layer to expose the conductive pattern, forming a lower electrode in the contact hole, forming a variable resistive oxide layer in the contact hole on the lower electrode, forming a middle electrode in the contact hole on the variable resistive oxide layer, forming a buffer oxide layer on the middle electrode and the insulation layer, and forming an upper electrode on the buffer oxide layer. Related resistive memory devices are also disclosed.