Field-effect transistor with multidielectric constant gate insulation layer

摘要

A field-effect transistor comprises a semiconductor substrate, a gate insulation film formed selectively on the semiconductor substrate, a gate electrode formed on the gate insulation film, source/drain regions formed in surface portions of the semiconductor substrate along mutually opposed side surfaces of the gate electrode, the source/drain regions having opposed end portions located immediately below the gate electrode, each of the opposed end portions having an overlapping region which overlaps the gate electrode, and a channel region formed in a surface portion of the semiconductor substrate, which is sandwiched between the opposed source/drain regions. That portion of the gate insulation film, which is located at the overlapping region where at least one of the source/drain regions overlaps the gate electrode, has a lower dielectric constant than that portion of the gate insulation film, which is located on the channel region. Thereby, a short channel effect can be fully suppressed, and a high-speed operation can be realized.