CoFeB/MgAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /CoFeB magnetic tunnel junctions (MTJs) with the barrier sputtered from sintered MgAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> target have been successfully fabricated. Dependence of tunneling magnetoresistance (TMR) ratio on both MgAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> deposition pressure and postannealing temperature has been studied. The TMR ratio of more than 50% at room temperature was obtained with an annealing temperature of 325 °C and MgAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> deposition pressure of 1.3 Pa. Temperature dependence of resistance in both parallel and antiparallel configurations can be well fitted by the model based on direct elastic tunneling and magnon-assisted inelastic tunneling. Inelastic electron tunneling spectroscopy (IETS) at low temperature, exhibiting three peaks originating from zero-bias anomaly, interface magnons, and barrier phonons, were measured and compared with the results of AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> and MgO-based MTJs. The IETS for all three types of MTJs shows quite similar peak positions for all kinds of elementary excitations except barrier phonons.