Al2O3 resistive random access memory (RRAM) with electroforming-free characteristics,high stability and uni-form properties is fabricated.The effect of the in situ hydrogen plasma enhanced treatment on the device performance is investigated.The dominated conduction mechanisms of the devices are ohmic behavior at low fields and space charge limited charge injection at high fields.The great improvement in the device properties is attributed to the hydrogen plasma treatment with the Al2O3 film,and this simple while effective atomic layer deposition based plasma treatment process is expected to be useful for other RRAM material systems as well.