Patent ID: 6979864
Filing Date: 2005-12-27
Classification: H01L

Abstract:
1. A power source unit comprising a circuit which outputs a constant voltage by comparing an output voltage with a reference voltage and which provides feedback of said output voltage to an input of said circuit, said circuit comprising: an LDMOS (lateral double-diffusion MOS) transistor, said LDMOS transistor comprising: a semiconductor substrate; a gate oxide layer formed on said semiconductor substrate having a uniform thickness; a gate electrode formed on said gate oxide layer; a drain well region of a first conductivity type formed in a region including said gate electrode; a channel well region of a second conductivity type opposite to that of said first conductivity type with an impurity concentration larger than that of said drain well region, formed in said drain well region having a partial overlap with said gate electrode; a source of said first conductivity type formed contiguously to one side of said gate electrode in said channel well region; a medium concentration drain region of said first conductivity type with an impurity concentration larger than that of said drain well region formed in said drain well region, having a partial overlap with another side of said gate electrode; and a drain of said first conductivity type with an impurity concentration larger than that of said medium concentration drain region, formed in said medium concentration drain region spatially separated from said gate electrode.