A RF ablation device includes a probe assembly that has an elongate cannula having a lumen disposed interiorly of an external wall of the cannula. The elongate cannula includes a plurality of slots formed within the external wall that provide access to the lumen. The probe assembly includes an electrode member that is slidably disposed within the elongate cannula, the electrode member including a plurality of tines configured for passage through the plurality of slots. The slots are disposed in a staggered arrangement or pattern about the external wall of the cannula. The staggered arrangement of slots may be used in a monopolar or bipolar arrangement of the electrodes on the cannula. A bipolar arrangement of electrodes using the staggered configuration produces larger ablation areas in a shorter period of time as compared to prior designs.