| 摘要 |
In a process for forming a CMOS integrated circuit (10) having polysilicon gate electrodes (28, 38) the polysilicon gate electrodes (28, 38) are simultaneously doped with impurities of a single conductivity type, independently of the semiconductor substrate (18). The invention enables the avoidance of the penetration problem which arises when boron is utilized to dope polysilicon. After forming the gate electrodes (28, 38) from a polysilicon layer (128), they are covered by a mask including a silicon oxide layer (130) and a silicon nitride layer (132). Then sources (22, 34) and drains (24, 32) of the n-channel and p-channel transistors (12, 14) are formed and an implantation or diffusion barrier (148) is grown over the sources (22, 34) and drains (24, 32). The mask (130, 132) is removed over the gate electrodes (28, 38) which are then doped with an n-type impurity. Polysilicon resistors (50) may be formed by initially doping the polysilicon layer (128) to a low level of conductivity and protecting the resistor areas (50) by a further mask (138), which may be of polysilicon or silicon nitride, during subsequent doping to a high level of conductivity. |
