Patent ID: 8102011

Claim:
A semiconductor device, comprising: a substrate; and a field effect transistor, wherein said field effect transistor includes: a channel region with a gate length “L” formed at a surface of said substrate; a gate electrode formed over said channel region; a source electrode and a drain electrode formed at both sides of said gate electrode; a low concentration region of a first conductivity type, which is formed in the surface of said substrate, said low concentration region being formed within said channel region; a drain-side diffusion region of a second conductivity type, which is formed in a surface of said low concentration region of said first conductivity type, said drain electrode being formed over a portion of a surface of said drain-side diffusion region; a source-side diffusion region of said second conductivity type, which is formed in a surface of said low concentration region of said first conductivity type, said channel region being formed between said drain-side diffusion region and said source-side diffusion region, said source electrode being formed over a portion of a surface of said source-side diffusion region; a first element isolation insulating layer which is formed over said drain-side diffusion region of said second conductivity type, isolates said drain-side diffusion region at the surface of said substrate and isolates said channel region from said drain electrode; a second element isolation insulating layer which is formed over said source-side diffusion region of said second conductivity type, isolates said source-side diffusion region at the surface of said substrate and isolates said channel region from said source electrode; and a high concentration region of said first conductivity type, which has an impurity concentration higher than the impurity concentration of said low concentration region, formed below said source-side diffusion region in said low concentration region of said first conductivity type over a range at least from a first end of said source-side diffusion region, said first end being distal from said channel region, to an end of said second element isolation insulating layer, said end being proximate to said channel region.