Apparent activation energy for the deposition of SiO2 films from tetraethylorthosilicate(TEOS)/O-2 discharges is calculated using the electron-induced dissociation model which describes the radical concentration in the steady state of a uniform plasma. The model is modified for a isobaric plasma to give the deposition rate of TEOS-SiO2 films as a function of the gas temperature adjacent to the substrate. In the scheme where organo-silane film precursors formed from TEOS completely cover the surface and thus the oxygen radical flux to the surface of growing films is the rate-limiting step, the model predicts that the apparent activation energies lie well in the range of -k(B)T(s) to -2k(B)T(s) (with k(B) the Boltzmann's constant and T-s the surface temperature, respectively), dependent on the discharge power, pressure, and the flow rate of reaction gases. The values of activation energy at T-s of 700 and 300 K are calculated to be -2.78 and -0.60 kcal/mol, respectively, which are consistent with those of estimated experimentally by other researchers. The model is further modified to attain a generalized form and on that basis the origin of the negative and temperature-dependent activation energy is discussed.