We report investigations of Si face 4H-SiC MOSFETs with aluminum ion implanted gate channels. High quality SiO2/SiC interface is obtained both when the gate oxide is grown on p-type epitaxial material and when grown on ion implanted regions. A peak field effect mobility of 170 cm(2)/VS is extracted from transistors with epitaxially grown channel region of doping 5x10(15) cm(-3). Transistors with implanted gate channels with aluminum concentration of 1x10(17) cm(-3) exhibit peak field effect mobility of 10(8) cm(2)/Vs, while the mobility is 62 cm(2)/Vs for aluminum concentration of 5x10(17) cm(-3). The mobility reduction with increasing acceptor density follows the same functional relationship as in n-channel Si MOSFETs.