High tunneling magnetoresistance (TMR) ratio and low RA in magnetic tunnel junctions are necessary condition for application in magnetic random access memory. To get high TMR ratio and low RA, good quality of MgO (002) insulating layer is important. To increase crystalline quality of MgO (002) layer, we applied negative bias on the substrate during MgO deposition. We report the results of the tunneling magnetoresistance (TMR) ratio and the resistance-area product (RA) for CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with substrate bias voltage, and showed TMR increase and RA decrease with substrate bias. The effects of substrate bias voltage on the TMR ratio, RA and MgO (002) peak intensity are discussed.