We report on the ferromagnetic characteristics of $Zn_{1-x}Mn_xO$ films (x = 0.3) prepared by sol-gel method on the silicon and (0001) ${alpha}-Al_2O_3$ substrates at the annealing temperature of 700$^{circ}C$. Magnetic measurements show that Curie temperature ($T_C$) and the coercive field ($H_C$) for the film on the silicon are about 32 K and about 275 Oe, while those for that on the sapphire are about 32 K and 425 Oe, respectively. Energy dispersive spectroscopy and transmission electron microscopy measurements suggest that ferromagnetic precipitates originated by manganese oxide compound formed at the interfaces of the both substrates may be responsible for the observed ferromagnetic behavior of the films. Electron paramagnetic resonance study of the powders up to the concentration of x=0.15 supports the result.