Method for detecting whether the alignment of bit line contacts and active areas in DRAM devices is normal, and a test device thereof. The method includes forming precursor layers that include a dopant rich layer and then annealing the precursor layers. The sensor is configured to measure a magnetic field in proximity to a current sensor of the electricity meter. At least one safety device is activated if the time remaining prior to the collision is shorter than or equal to at least one of the activation times of the actuators. As a result, excessive electric charge can be released effectively in the double gate structure while suppressing an increase in capacitor between the pixel electrode and the signal line.