In the multi-level wiring structure in ultra-large-scale integration circuits, a bottleneck against high-speed operation of the elements is the capacitance between wires. If the capacitance between wires is to be decreased, the dielectric constant of an interlayer insulating film must be reduced. Among the low-dielectric-constant films, the SiOC(-H) film is an appropriate materials for the advanced Cu interconnects applications. In this study, we report the mechanical properties of SiOC(-H) thin films prepared with different substrate temperatures and deposited on p-type Si(100) substrates by using plasma-enhanced chemical vapor deposition (PECVD) with dimethoxy-dimethylsilane (DMDMS, C 4H12O2Si) and oxygen gas as precursors. Nanoindentation studies were carried out in order to determine the mechanical properties of the SiOC(-H) films. The hardness and the elastic modulus of SiOC(-H) films prepared with different substrate temperatures were measured to be in the range of 2.25 - 4.5 and 20 - 35 GPa, respectively. The values of hardness and elastic modulus were observed to increase with increasing of substrate temperature. In the SiOC(-H) film, the -CH3 group, as an end group, was broken when the substrate temperature was increased, thereby reducing the film's density to increase the values of the mechanical properties. FTIR spectroscopy studies were carried out in the absorbance mode in the range of 400 to 4000 cm-1, which showed various bonding configurations, such as the Si-O-Si(C), the Si-CH3, the -OH, the CHn bonds in the films. The dielectric constant of the SiOC(-H) films was investigated using a metal-insulator-semiconductor [MIS, Al/SiOC(-H)/p-Si(100)] structure at a 1 MHz frequency.