Highly sensitive sensors based on capacitance changes have been developed for the detection of heavy metal ions by utilization of self-assembled monolayer films on silicon oxide surfaces between interdigitated electrodes. The attractive ability of the sensor to efficiently preconcentrate trace amounts of Cu2+ allows a simple and ultrasensitive method for copper ion detection. The wide range linear calibration curve of 1.0 x 10(-13) to 1.0 x 10(-9) M Cu2+ is constructed at 53 Hz. This sensor is highly sensitive and can Push the detection limit of copper ion down to 1.0 x 10(-13) M.