Thin silicon dioxide films were prepared by photo chemical vapor deposition. IR absorption and Auger electron spectroscopy have shown that the dominant components of the oxide are silicon and oxygen with little amount of hydrogen. MIS capacitors were constructed on InSb substrates. C-V characteristics of the MIS capacitors were measured, and mid-gap interface state density of low 10**1**2 cm** minus **2eV** minus **1 was determined. The amount of hysteresis observed was found to be about 10% of the inversion bias voltage. Annealing studies were also conducted to improve the electrical properties. After annealing, mid-gap interface state density was reduced to 5 multiplied by 10** minus **1**1 cm** minus **2eV** minus **1 and the amount of hysteresis reduced to 5% of the inversion bias voltage.