A method of making a monolithic three dimensional NAND string, comprising: providing a stack of alternating first material layers and second material layers over a substrate, wherein the first material layers comprise an insulating material and the second material layers comprise sacrificial layers; forming a first side opening in the stack on a first side of a stack portion; selectively removing the second material layers through the first side opening to form first side recesses between adjacent first material layers; forming a blocking dielectric inside the first side recesses and the first side opening, the blocking dielectric having a clam shaped regions inside the first side recesses; forming a first barrier layer over the blocking dielectric inside the first side recesses and the first side opening; and forming a plurality of copper control gate electrodes in the respective clam shell shaped regions of the blocking dielectric in the first side recesses; wherein: the first barrier layer has clam shaped regions inside the clam shaped regions in the blocking dielectric the first side recesses; and the plurality of copper control gate electrodes are formed in the respective clam shell shaped regions of the first barrier layer in the first side recesses; the method characterized in that forming a plurality of copper control gate electrodes comprises: forming a sacrificial film on the first barrier layer in the first side opening and the first side recesses, wherein the first barrier layer is a copper nucleation layer; anisotropically etching the sacrificial layer in the first side opening and recessing the sacrificial layer in the first side recesses to expose the first barrier layer in the first side opening and a portion of the first barrier layer in the first side recesses; oxidizing the exposed first barrier layer in the first side opening and the first side recesses; removing the sacrificial layer to expose the remaining first barrier layer in the first side recesses; and selectively electrochemically depositing copper on the remaining first barrier layer using the first barrier layer as a copper nucleation layer without depositing copper on the oxidized portions of the first barrier layer. providing a stack of alternating first material layers and second material layers over a substrate, wherein the first material layers comprise an insulating material and the second material layers comprise sacrificial layers; forming a first side opening in the stack on a first side of a stack portion; selectively removing the second material layers through the first side opening to form first side recesses between adjacent first material layers; forming a blocking dielectric inside the first side recesses and the first side opening, the blocking dielectric having a clam shaped regions inside the first side recesses; forming a first barrier layer over the blocking dielectric inside the first side recesses and the first side opening; and forming a plurality of copper control gate electrodes in the respective clam shell shaped regions of the blocking dielectric in the first side recesses; the first barrier layer has clam shaped regions inside the clam shaped regions in the blocking dielectric the first side recesses; and the plurality of copper control gate electrodes are formed in the respective clam shell shaped regions of the first barrier layer in the first side recesses; the method characterized in that forming a plurality of copper control gate electrodes comprises: forming a sacrificial film on the first barrier layer in the first side opening and the first side recesses, wherein the first barrier layer is a copper nucleation layer; anisotropically etching the sacrificial layer in the first side opening and recessing the sacrificial layer in the first side recesses to expose the first barrier layer in the first side opening and a portion of the first barrier layer in the first side recesses; oxidizing the exposed first barrier layer in the first side opening and the first side recesses; removing the sacrificial layer to expose the remaining first barrier layer in the first side recesses; and selectively electrochemically depositing copper on the remaining first barrier layer using the first barrier layer as a copper nucleation layer without depositing copper on the oxidized portions of the first barrier layer. forming a sacrificial film on the first barrier layer in the first side opening and the first side recesses, wherein the first barrier layer is a copper nucleation layer; anisotropically etching the sacrificial layer in the first side opening and recessing the sacrificial layer in the first side recesses to expose the first barrier layer in the first side opening and a portion of the first barrier layer in the first side recesses; oxidizing the exposed first barrier layer in the first side opening and the first side recesses; removing the sacrificial layer to expose the remaining first barrier layer in the first side recesses; and selectively electrochemically depositing copper on the remaining first barrier layer using the first barrier layer as a copper nucleation layer without depositing copper on the oxidized portions of the first barrier layer.