Anodic bonding is usually used in typical bulk micromachined pressure sensors. In this study, pressure sensors were fabricated by the 6-inch silicon direct bonding method. Silicon direct bonded wafers can yield approximately four times the number of chips than anodically bonded wafers. Equations are derived to compare the sizes of the chips obtained by the different methods. It is revealed that silicon direct bonding is particularly suitable in high-pressure applications and thick wafers. When contacted to form a pair, voids are sometimes observed upon inspection. Large voids did not change significantly, and it was also found in the experiment that small voids (<6 mm) disappeared after the hightemperature annealing process. Three major defects which are cracked membranes, broken membranes, and peeling at the wafer edge, were observed during the grinding of the sensing wafers.