An ultrafast lateral silicon PiN diode with geometric traps is proposed using a silicon-on-insulator (SOI) substrate with the traps. The proposed diode successfully suppresses waveform oscillation because the trapped hole suppresses electric field penetration and prevents the oscillation trigger known as "dynamic punch-through." Because of the short current path caused by the oscillation prevention, the reverse recovery speed was higher and the reverse recovery loss was strongly reduced. The proposed trap structure and design method would contribute to performance improvement of all power semiconductor devices including IGBTs and power MOSFETs. (C) 2014 Elsevier Ltd. All rights reserved.