An alternating stack of insulating layers and sacrificial material layers is formed on a substrate. Separator insulator structures can be optionally formed through the alternating stack. Memory opening are formed through the alternating stack, and the sacrificial material layers are removed selective to the insulating layers. Electrically conductive layers are formed in the lateral recesses by deposition of at least one conductive material. Metal-semiconductor alloy regions are appended to the electrically conductive layers by depositing at least a semiconductor material and inducing reaction of the semiconductor material with the material of the electrically conductive layers and/or a sacrificial metal layer. Memory stack structures can be formed in the memory openings and directly on the metal-semiconductor alloy regions of the electrically conductive layers.