A bidirectional SCR device (LCDDSCR) with low trigger voltage and low capacitance has been designed to meet the increasing demands of system design for ESD protection, particularly in relation to the transmission rate and signal frequency of data interfaces, based on a 0.5 μm BCD process. Compared to the conventional bi-directional SCR device structure (DDSCR), the LCDDSCR structure employs the critical diffusion technique to reduce the area of the P-well region, thereby lowering the device's input capacitance. Additionally, the ZP region is introduced using the critical Zener injection technique to reduce the trigger voltage, based on the Zener triggering characteristics of the SCR device. Transmission line pulse (TLP) test and capacitance test results show that the LCDDSCR device has a trigger voltage of 7.5 V, a sustaining voltage of 1.5 V, a junction capacitance of 0.53 pF, and a peak inrush current of 7 A (0.53 pF/7 A), which satisfies the requirements for ESD protection and exhibits excellent low capacitance and low trigger voltage characteristics.