CMOS device with high and low voltage transistors.

摘要

A semiconductor device having high (76,88) and low voltage (80,84) transistors on the same chip. High voltage NMOS transistor (76) comprises a polysilicon gate (40) doped at a first dopant level. Low voltage NMOS transistor (80) comprises a polysilicon gate (44) doped at a second dopant level. The second dopant level is higher than the first. High voltage PMOS transistor (84) comprises a polysilicon gate (48) doped at a third dopant level. Low voltage PMOS (84) transistor comprises a polysilicon gate (52) doped at a fourth dopant level. The fourth dopant level is higher than the third. By allowing the electric field to penetrate into the bottom of the high voltage transistor gate, the effective oxide thickness is made greater.