The present disclosure relates to a magnetic tunnel junction (MTJ) device and its fabricating method. Through forming MTJ through a damascene process, device damage due to the etching process and may be avoided. In some embodiments, a spacer is formed between a first portion and a second portion of the MTJ to prevent the tunnel insulating layer of the MTJ from being damaged in subsequent processes, greatly increasing product yield thereby. In other embodiments, signal quality may be improved and magnetic flux leakage may be reduced through the improved cup-shaped MTJ structure of this invention.