The present study aimed to investigate chemical vapor deposition of Ge thin films using GeO2 and C2H5OH (ethanol) as precursors. Thermodynamic analysis predicted that GeO2 was reduced to gaseous GeO and solid Ge by the species (mainly H-2, CO, CH4) generated by the ethanol decomposition at 900-1200 K. Experimentally, the reaction of the GeO2 powder with the ethanol-derived species was studied at these temperatures. Significant mass loss was observed above 1000 K due to gaseous GeO production. It was determined that the reduction process might be controlled by the chemical reaction kinetics at 900 K and by the external mass transport of gaseous species at 1000-1200 K. Metallic Ge was not detected in the residues. Ge was, however, deposited on a Si substrate positioned by the downstream side of the reaction tube at 723 K, while GeO2 reacted with the species generated by the ethanol decomposition at 1000-1200 K (the source temperatures). Ge coverage on the Si substrate increased with source temperature due to enhanced GeO supply. Ge thin film with a thickness of 4 was obtained when the source temperature was 1200 K. The reduction of GeO2 to GeO and Ge was discussed in terms of open-tube flow and the thermodynamic analysis.