Method of manufacturing semiconductor device

Abstract

Disclosed is a method of manufacturing a semiconductor device which includes a source region, a channel region, a drain region, a gate electrode formed on the channel region through a gate insulating film 6 and a drift region (N− layer 22) formed between the channel region and the drain region, wherein the process of forming the drift region (N− layer) comprises the steps of: ion-implanting and diffusing at least two kinds of second conduction type impurities (e.g. phosphorus and arsenic ions) having different diffusion coefficients in a P-type well region 21; ion-implanting at least one kind first conduction type impurities (e.g. boron ions) having a diffusion coefficient substantially equal to or larger than that of at least one of said second conduction type impurities (e.g. phosphorus); and diffusing the first conduction type impurities after the gate insulating film 6 has been formed.

Dependencies are inferred from the claim text.