Nowadays, the main important issue for power supplies designers is to feed last generation of microprocessors and DSPs, since they require high current slew rates on accompain with low output voltage. The most important issue with these power supplies is the efficiency, especially with ultra-high switching frequency. The main factor of limitation for these target systems with ultra-high switching frequency is the switching losses and body-diode losses. Zero-Voltage-Switching Quasi-Square-Waveform (ZVS-QSW) has been proposed to solve the matter of switching losses; however, it can not achieve that for wide-load applications. Besides, adaptive technique has been introduced to reduce the body-diode losses. In this paper, in this paper the advantage of the two techniques is assumed by merging them together. Moreover, a modification circuit is proposed to apply soft-switching technique for the main switch. In conclusion, novel soft switching technique is proposed for high-switching frequency synchronous buck converter based on ZVS_QSW and adaptive technique. The mathematical model is introduced and confirmed using PSIM simulation using 5MHz synchronous model.