This paper presents the dc and high-frequency performances of laterally diffused metal-oxide-semiconductor (LDMOS) transistors with superjunction (SJ) structures. The SJ-LDMOS transistors were fabricated using a 0.5-μm CMOS process. By utilizing a modified SJ/RESURF layout (Type I) or a tapered SJ layout (Type II) in our devices, better high-frequency performances and higher breakdown voltages are achieved compared with conventional SJ counterpart, owing to the suppression of the substrate-assisted depletion effect and the reduction of the drain resistance. For Type I device with an optimal SJ layout dimension, the cutoff frequency and the breakdown voltage are 3.7GHz and 68 V, respectively. For Type II device with a smallest p-pillar width near the drain, they can be enhanced further and reach to 4.9 GHz and 83V. These experimental results suggest that the SJ-LDMOS can be used in the RF power amplifiers.