For the first time, SOI-emitter switched thyristors (SOI-ESTs) with forward blocking capability of 600 and 1500 V have been fabricated. In these devices, the lateral turn-off transistor of the EST is separated dielectrically from the vertical thyristor using SIMOX Separation by Implanted Oxygen technology. By this method, the parasitic thyristor inherent to other ESTs is totally eliminated. The effects of parametrical variations on the output characteristics of the SOI-EST are discussed.