Ruthenium dioxide (RuO2) thin films can be used as the electrode material for future technology nodes. In this work, atomic layer deposition (ALD) was used to deposit thin films of RuO2 on SiO2 using bis-(ethylcyclopentadienyl)-ruthenium [Ru(EtCp)2] as the precursor and oxygen (O2) plasma as the reducing agent. The thermal stability of the deposited films were investigated in the N2 ambient and in the forming-gas environments using rapid thermal processing (RTP). High-resolution transmission electron microscope (HR-TEM) and atomic force microscopy (AFM) were also employed to explore the growth mechanism of the RuO2 thin films on SiO2.