The present invention relates to a method, device, and system for improved mapping and/or ablation of a tissue. The device may generally include an elongate body and a distal assembly affixed to the elongate body that includes a treatment electrode having a conductive mapping region and a selectively conductive ablation region that is conductive of high-frequency current and substantially non-conductive of low-frequency current. Alternatively, the device may generally include a treatment electrode having a conductive mapping or ablation region and a region that is coated with an electrically insulated but thermally conductive layer.