Abstract: In manufacturing a semiconductor device, the thickness of source and drain regions is maintained equal by performing the same number of etching steps on each source and drain region. This procedure can be applied to various types of semiconductor devices, such as a memory cell transistor of a DRAM, stack-type memory cell transistor of a DRAM, a peripheral circuit of a DRAM, a semiconductor device formed on an SOI structure, and a trench-type memory cell of a DRAM formed on an SOI structure. By maintaining the source and drain regions at the same thickness, the resistance values are maintained, thereby avoiding deterioration of the transistor characteristics.