A high speed tunnel current measurement technique called HSTCM has been proposed for characterizing insulating thin films. A voltage pulse (less than 100 µs) is applied across an insulator and a current pulse is measured using a specially devised operational amplifier. This technique enables measurement of high electric field current to voltage (I-V) characteristics of thin SiO2 films in electric fields up to 2 GV/m, and to measure time dependent tunnel current characteristics in insulators, such as a Si3N4-SiO2 two-layer insulator of an MNOS (Metal Nitride Oxide Semiconductor) device, in the 10 µs-1 ms range. Accurate high electric field I-V characteristics in thin SiO2, and a capacitor coupled model for a floating gate non-volatile memory device could provide a high-precision simulation program for write/erase characteristics for the memory device. Furthermore, high speed time-dependent tunnel current measurement enables characterization of transient carrier trap phenomena in the insulator of the MNOS device in the µs range, i.e., the device's actual operation period. As described above, the HSTCM technique is a strong tool for evaluating tunneling phenomena in various insulating films and the operation of non-volatile memory devices.