A method of forming a magnetoresistive memory device includes forming a ferromagnetic layer, forming a tunneling barrier layer on the ferromagnetic layer, forming a first preliminary free magnetic layer (free layer) containing boron (B) on the tunneling barrier layer, forming a first buffer layer on the first preliminary free layer, performing a first annealing process to transition the first preliminary free layer to form a second preliminary free layer and the first buffer layer to form a first boride layer, performing an etching process to remove the first boride layer, forming a second buffer layer on the second preliminary free layer, performing a second annealing process to transition the second preliminary free layer to form a free layer and the second buffer layer to form a second boride layer, and performing an oxidation process to transition the second boride layer to an oxide layer.