In this paper, polyimide thin films are fabricated by vapor deposition polymerization method appling to the interlayer insulator of semiconductor device, and are investigated in detail. It is found that the packing density and uniformity of films deposited by thermal evaporation are increased according to curing temperature. The resistivity, breakdown strength, relative permitivity, and dielectric loss are $3.2 omes10^{15}Omega$cm, 4.61 MV/cm, 2.9(10kHz) at $25^{circ}C$, respectively. This thin films can be endured at $230^{circ}C$ for 20,000 hours. Finally, we conclude that the thin films having the characteristics similar to those of $SiO_2$ can be used as an insulation films between layers of semiconductor device.