A method of making high voltage complementary bipolar and BiCMOS devices on a common substrate. The bipolar devices are vertical NPN and PNP transistors having the same structure. The fabrication process utilizes trench isolation and thus is scalable. The process uses two epitaxial silicon layers to form the high voltage NPN collector, with the PNP collector formed from a p-well diffused into the two epitaxial layers. The collector contact resistance is minimized by the use of sinker up/down structures formed at the interface of the two epitaxial layers. The process minimizes the thermal budget and therefore the up diffusion of the NPN and PNP buried layers. This maximizes the breakdown voltage at the collector-emitter junction for a given epitaxial thickness. The epitaxial layers may be doped as required depending upon the specifications for the high voltage NPN device. The process is compatible with the fabrication of low voltage devices, which can be formed by placing the sinker regions under the emitter region. The thicknesses of the two epitaxial layers may be adjusted as required depending upon the specifications for the low voltage devices.