We have investigated the fracture behavior of tetrahedral amorphous carbon films, with thicknesses 0.15 (ultrathin), 0.5 (thin), and 1.2 (thick) microns on silicon substrates. To that end, the systems were progressively loaded into a nanoindenter using a spherical tip, and surface and cross sections were subsequently examined using a focused ion beam miller at different loads. A transition was found as a function of film thickness: for ultrathin and thin films, cracking (radial and lateral) initiated in the silicon substrate and followed a similar path in the films. Thicker films, on the other hand, provided a higher level of protection to the substrate, and cracking (lateral and radial at the interface) was constrained to the film. The damage modes and the transition obtained differ from those that occur in thick coatings. Lateral cracks are highly dangerous, leading to delamination of thick films and to spallation when thinner films are used. The results have implications concerning the mechanical reliability of microelectromechanical systems.