The rare-earth nickelates (LnNiO3, Ln = lanthanide) are interesting from both fundamental and applied perspectives, but synthesis remains a bottleneck to research due to their thermodynamic instability. Here we report the synthesis of SmNiO3 thin films on oxidized silicon wafers by physical vapor deposition followed by high pressure oxygen annealing at intermediate temperatures. The high pressure annealed films show an insulator–metal transition characteristic of bulk samples. Our experimental observations then allow us to estimate bounds on the phase stability regime, which are particularly useful given the dearth of direct thermodynamic data available for LnNiO3. We examine the limitations of these thermodynamic analyses applied to ultra-thin films. The stabilization of SmNiO3 on a canonical semiconductor template creates opportunities to study the utility of the above room temperature insulator–metal transition (at TIM = 400 K) in electronic devices.