A step-like change in the interface built-in potential by controlling the ferroelectric polarization has been observed in PLZT thin film sputtered on GaAs single crystal heterostructure junction. We have developed a nonvolatile memory FET by using this MFS (Metal-Ferroelectric-Semiconductor) construction. A typical performance of the GaAs device with a p-channel mode operation is that the writing ("0" to "1" threshold) gate voltage Von=1.5 V, the erasing ("1" to "0") gate voltage Voff=6.0 V, and the on state drain current Ion=0.1 mA. This operation power level obtained here is about one order of magnitude smaller than that of similar type devices using other ferroelectrics such as Bi4Ti3O12, PZBFN and SbSI. A series of technical data for the fabrication technologies including thin film deposition of the ferroelectric are presented, and the analyses on the device performance are also discussed.