A method of forming a MEMS device includes providing a substrate having a device stopper. The device stopper is integral to the substrate and formed of the substrate material. A thermal dielectric isolation layer may be arranged over the device stopper and the substrate. A device cavity may be formed in the substrate and the thermal dielectric isolation layer. The thermal dielectric isolation layer and the device stopper at least partially surround the device cavity. An active device layer may be formed over the thermal dielectric isolation layer and the device cavity.