Recently, a method to switch the magnetization direction of nanomagnets with perpendicular anisotropy using spin-orbit torque (SOT) assisted by the Dzyaloshinskii–Moriya interaction (DMI) was proposed. However, in this method, the duration of current pulse cannot be precisely controlled for magnetization switching, and the switching probability does not reach 100%. In this article, we propose a method to reduce the width of current-carrying wire (i.e., electrode) below the nanomagnet size and confirm the validity of this method using micromagnetic simulations. Our simulation results show that magnetization switching does not depend on the duration of current pulse, and a switching probability of 100% can be achieved by using a current wire of appropriate width.