The paper describes a new fabrication technology for a monolithic high-power linear IC. It is based on a novel process for controlling the epitaxial growth of single crystal regions and very fine polycrystalline regions on an IC substrate essentially in accordance with the specified mapping of the IC pattern. Polycrystalline regions are used in areas of isolation and collector lead paths which must be diffused deeply, and contribute to the most important characteristics required for the high-power IC, i.e., higher breakdown voltage and lower saturation resistance. A power capability far beyond any known in this field has been achieved. A typical example of the output power rating for an IC designed for use in a low-frequency SEPP-type power amplifier is 20-watts rms continuous service, and the total harmonic distortion content is less than 8 percent at 1 kHz at 40-volts source voltage.