Gate Structure for Midgap Gate CMOS
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
A new gate structure, employing a thin buffer layer of undoped poly in between the gate oxide and mid-gap gate material, is proposed. The thin undoped poly layer which is completely depleted insures a reliable gate-oxide interface, while it is transparent to the work function of the mid-gap gate. For the sub 0.5 mm CMOS technology the gate material has to be different from the n+poly which is presently used in 1 mm CMOS technology. The major reason is the work function of the n+poly (Z4.2 eV) which is too low for sub 0.5 mm devices. One of the candidates for the new gate material is the mid-gap material (dmZ4.75 eV) such as tungsten or tungsten silicide. A major problem with this mid-gap gate material is the reliability of the gate-oxide interface. In this article the structure shown in Fig. 1 is proposed for the sub 0.