High performance mosfet with modulated channel gate thickness

Abstract

A semiconductor device having gate oxide with a first thickness and a second thickness is formed by initially implanting a portion of the gate area of the semiconductor substrate with nitrogen ions and then forming a gate oxide on the gate area. Preferably the gate oxide is grown by exposing the gate area to an environment of oxygen. A nitrogen implant inhibits the rate of SiO growth in an oxygen environment. Therefore, the portion of the gate area with implanted nitrogen atoms will grow or form a layer of gate oxide, such as SiO , which is thinner than the portion of the gate area less heavily implanted or not implanted with nitrogen atoms. The gate oxide layer could be deposited rather than growing the gate oxide layer. After forming the gate oxide layer, polysilicon is deposited onto the gate oxide. The semiconductor substrate can then be implanted to form doped drain and source regions. Spacers can then be placed over the drain and source regions and adjacent the ends of the sidewalls of the gate.