We investigate the effect of annealing temperature on the characteristics of solution-processed indium oxide (In2O3) films. From thermogravimetric analysis of the precursor solution, annealing temperatures of 150, 350, and 450 degrees C are adopted. The In2O3 films are analyzed by ultraviolet/visible spectroscopy, atomic force microscopy, grazing incidence X-ray diffraction, and Hall-effect measurement. Raman spectroscopy is used to examine the crystal polymorphism of the solution-processed films. Experimental results suggest that the optimal annealing temperature can be 350 degrees C. The transistor with the In2O3 semiconductor annealed at 350 degrees C exhibits the field-effect mobility of 1.4 V/cm(2) and on/off ratio of 2.1 x 10(6).