Filamentary bilayer ReRAMs based on conductive metal-oxide (CMO) / HfOx have gained potential for applications in the field of analog in-memory computing. Compared to conventional metal / HfOx based system, the resistive switching graduality improves and the switching stochasticity decreases. In this work we replace a standard Ti scavenging layer of an HfOx-based ReRAM with a conductive metal-oxide such as TaOx. We assess the material stack structural and electrical properties and identify an onset layer of oxidized metal-oxide at the interface between the dielectric and the CMO layer. We discuss its presence in relation to the increased forming voltage of the bilayer devices, the ON/OFF ratio, and the resistive switching window. Our scaled (1 μm2) bilayer ReRAM has excellent analog properties (at least 4 bits) and good retention measured for a minimum of 30 min. All materials and fabrication steps are compatible with complementary-metal-oxide-semiconductor (CMOS) and the back-end-of-the-line (BEOL) processes.