Abstract Low-density materials, such as the commercially available hydrogen silsesquioxane (HSQ) offer a low dielectric constant. Thus HSQ with a low value of k (∼2.85) can be spin-coated if the density of Si H bonding is maintained at a high level and the formation of OH bonds and absorption or creation of water in the film is minimized. O2 plasma exposure on HSQ film properties increases leakage current of metal/HSQ/Si/metal structures. Also the dielectric constant shows a significant increase after O2 plasma exposure. Another important consequence of the O2 plasma exposure is the large decrease in the contact angle of the HSQ surface. In this paper, we demonstrate first damage repair process involving trimethylchlorosilane (TMCS) treatment for 10 min at atmospheric pressure leads to a regain of a leakage current density and dielectric which approach values very near to the as-deposited film. These results show that the TMCS treatment is a promising technique to repair the damage even in the commercially available and highly applicable low-k material and increase the visibility of its use at the 0.1 μm technology. The increase of the hydrophilic nature of the surface after O2 plasma exposure leads to increase absorption of moisture with a subsequent increase in the dielectric constant.