Patent ID: 6943116

Claim:
A method for fabricating a p-channel field-effect transistor, which comprises the steps of: providing a semiconductor substrate; doping the semiconductor substrate with donors by performing a first implantation for forming an n-doped well; carrying out a thermal oxidation for forming a thin oxide layer on a surface of the semiconductor substrate; nitriding the oxide layer in an N 2 O atmosphere to control a permeability of the oxide layer with respect to one of boron and boron fluoride particles penetrating through the oxide layer; depositing a first layer formed from n-doped polysilicon above the oxide layer; p-doping the first layer with particles selected from the group consisting of boron particles and boron fluoride particles, a p-type dopant concentration of the particles being lower than an n-type dopant concentration of the first layer; carrying out a lithographic projection step and an etching step for removing the first layer in a first and a second region and for forming an n-doped gate electrode in a third region located between the first and second regions on the semiconductor substrate; doping the semiconductor substrate with acceptors by performing a second implantation for forming a p-doped source region in the first region and a p-doped drain region in the second region in the semiconductor substrate; and exposing the semiconductor substrate to a temperature elevated to such an extent that a number of the particles migrate from the first layer through the oxide layer into the semiconductor substrate for forming a p-doped zone within the n-doped well for defining a threshold voltage of the field-effect transistor.