A prototype MFSFET using ferroelectric fluoride BaMgF$_4$as a gate insulator has been successfully fabricated with the help of 2 sheets of metal mask. The fluoride film was deposited in an ultrai-high vacuum system at a substrate temperature of below 30$0^{circ}C$ and an in-situ post-deposition annealing was conducted for 20 seconds at $650^{circ}C$ in the same chamber. The interface state density of the BaMgF$_4$/Si(100) interface calculated by a MFS capacitor fabricated on the same wafer was about 8$ imes$10$^{10}$ /cm$^2$.eV. The I$_{D}$-V$_{G}$ characteristics of the MFSFET show a hysteresis loop due to the ferroelectric nature of the BaMgF$_4$film. It is also demonstrated that the I$_{D}$ can be controlled by the “write” plus which was applied before the measurements even at the same “read”gate voltage.ltage.