Abstract: A method for manufacturing input/output port devices of a semiconductor circuit having low body effect, suitable for use on a semiconductor substrate on which a plurality of pull-up device regions and pull-down device regions are formed. First, when executing a channel implantation, an anti-punchthrough implantation, and a threshold adjustment implantation, a mask which masks PMOS devices in the CMOS process is used to mask pull-up device regions on a semiconductor substrate. Furthermore, when executing a cell implantation, a mask which masks the outside regions of memory cells is used to mask pull-down device regions. In the invention, the body effect of pull-up devices on the input/output port is reduced without using any extra mask and under the original process, thereby lowering the threshold voltage and reducing the output voltage drop.