MOSFET transistor cell manufactured with selectively implanted punch through prevent and threshold reductoin zones

摘要

A n-channel MOSFET device is formed with a selective high energy boron implantation into the N region of the n- channel where a photoresist is employed to cover the central portion over the channel. Small n- regions are formed near the channel source interface. These small n- regions have the advantages of preventing punch through. The selective implant regions have the additional advantages that the JFET resistance is not increased as a result of forming a punch through prevention region near the source channel boundary. Also disclosed in this invention is a p-type DMOS where a novel boron implantation is applied to reduce the threshold voltage. The boron is selectively implanted into the n-type channel near the source, i.e., a threshold sensitive region. The threshold voltage is reduced without unduly lowering the drain to source breakdown voltage.