Method of making metal oxide semiconductor field effect transistor

A method of making a metal oxide semiconductor field effect transistor comprising the steps of;

• forming a field region in a substrate of a first conductivity type to define the field region and an active region;
• forming a gate oxide film on the active region;
• implanting an impurity in the active region to control a threshold voltage;
• forming a polysilicon film over the whole surface of the substrate;
• etching the polysilicon film and the gate oxide film to form the gate electrode on the active region;
• forming a thin insulating film over the whole surface of the substrate;
• forming a semiconductor layer on the thin insulating film;
• anisotopically etching the thin insulating film and the semiconductor layer with a RIE method to form sidewall spacers at side surfaces of the gate electrode and the gate oxide film;
• implanting a high concentration impurity of a second conductivity type to form high concentration source/drain regions of a second conductivity type, by self-aligning with the sidewall spacers as a mask;
• removing the semiconductor layer for sidewall spacers;
• forming a thick insulating film and a gate cap insulating film;
• removing the thin insulating film for sidewall spacers;
• and implanting a low concentration impurity of a second conductivity type and a low concentration impurity of a first conductivity type self-aligning with the gate electrode and the thick insulating film as a mask, to form low concentration source/drain regions of a second conductivity type coming into contact with high concentration source/drain regions and to form a low concentration impurity region of a first conductivity type enclosing low concentrating source/drain regions of the second conductivity type, in the active region.