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We propose and demonstrate a low-cost CMOS-compatible step-gate-oxide (SGO) SOI MOSFET that is suitable for RF power amplifiers in short- and medium-range wireless applications. The device structure and fabrication are identical to those of the standard SOI MOS devices except that the gate oxide features a step structure that consists of a thin oxide region on the source side and a thick oxide region on the drain side. A well-designed and optimized SGO SOI MOSFET with appropriate thin/thick gate length ratio exhibits improved breakdown voltage without adverse effects on the drain current characteristics. The step-gate-oxide structure also features reduced gate capacitances, leading to higher cutoff frequencies. The SGO MOSFET power amplifiers can be integrated with other CMOS-based RF blocks for single-chip RF transceivers.