The authors describe a method to electrically adjust the spring constant of an active atomic force microscopy (AFM) probe using electrostatic spring softening effect. The probe consists of a clamped membrane with interferometric displacement sensing and integrated electrostatic actuation. Using the bias voltage on the integrated electrostatic actuator, the spring constant of the probe is reduced electrically. This increases the force sensitivity of the probe without significant dimensional change, therefore not affecting its noise level. The sensitivity improvement for force spectroscopy is demonstrated by capturing force curves using the membrane probe while it is in interaction with an AFM tip.