A semiconductor device includes a semiconductor layer laminate disposed on a semiconductor substrate, a first and a second low-side transistors, and a first and a second high-side transistors. Each of the transistors is disposed on the semiconductor layer laminate, and includes a gate electrode, a source electrode, and a drain electrode. The second low-side transistor is disposed between the first low-side transistor and the first high-side transistor, and the first high-side transistor is disposed between the second low-side transistor and the second high-side transistor. The source electrodes of the first and the second low-side transistors are combined into one source electrode, the drain electrodes of the first and the second high-side transistors are combined into one drain electrode, and the drain electrode of the second low-side transistor and the source electrode of the first high-side transistor are combined into one first electrode.