AbstractDevelopment of a high‐frequency, high‐power transistor is expected for communication and broadcast usages. In recognition of superior high‐frequency performance and thermal stability of the lateral power MOSFET, the authors have attempted to improve power and frequency characteristics. By means of the self‐align method using high melting point, 1.5‐μm metal gate, a high‐frequency characteristic of a cutoff frequency of 4 GHz was attained.Since the high output power depends on high breakdown voltage and low on‐resistance, the trade‐off between the breakdown voltage of 100 V and the on‐resistance was carried out using two‐dimensional analysis. Based on the findings, a chip was fabricated which has a saturation output power of 50 W and a drain efficiency of 50 percent at 860 MHz.Further, the output was increased by the parallel operation of multichips containing an internal matching circuit. With three chips, an output power of 100 W, a power gain of 12 dB, and a drain efficiency of 45 percent were attained. With a four‐chip push/pull configuration, an output power of 150 W, a power gain of 12 dB and a drain efficiency of 47 percent were attained.