As　an　industry　accepted　storage　scheme,　hafnium　oxide　(HfOx)　based　resistive　random　access　memory　(RRAM)　should　further　improve　its　thermal　stability　and　data　retention　for　practical　applications.　We　therefore　fabricated　RRAMs　with　HfOx/ZnO　double-layer　as　the　storage　medium　to　study　their　thermal　stability　as　well　as　data　retention.　The　HfOx/ZnO　double-layer　is　capable　of　reversible　bipolar　switching　under　ultralow　switching　current　(＜　3　μA)　with　a　Schottky　emission　dominant　conduction　for　the　high　resistance　state　and　a　Poole-Frenkel　emission　governed　conduction　for　the　low　resistance　state.　Compared　with　a　drastically　increased　switching　current　at　120　°C　for　the　single　HfOx　layer　RRAM,　the　HfOx/ZnO　double-layer　exhibits　excellent　thermal　stability　and　maintains　neglectful　fluctuations　in　switching　current　at　high　temperatures　(up　to　180　°C),　which　might　be　attributed　to　the　increased　Schottky　barrier　height　to　suppress　current　at　high　temperatures.　Additionally,　the　HfOx/ZnO　double-layer　exhibits　10-year　data　retention　@85　°C　that　is　helpful　for　the　practical　applications　in　RRAMs.　©　2017　Chinese　Physical　Society　and　IOP　Publishing　Ltd.