Semiconductor device and process for manufacturing the same

Abstract

A semiconductor device has a semiconductor substrate of the first conductivity type, a gate electrode buried in a groove formed in an element region of the substrate, first source and drain regions of the second conductivity type formed in surface regions of the semiconductor substrate on either side of the gate electrode, and second source and drain regions each having a concentration higher than that of each of the first source and drain regions, the second source and drain regions being formed in the surface regions of the semiconductor substrate on either side of the gate electrode, spaced away from the gate electrode, and adjacent to the first source and drain regions, respectively. This semiconductor device has a structure wherein the gate electrode is deeply buried in the substrate. Therefore, a short channel effect can be prevented. The gate electrode buried in the groove extends through the semiconductor region, having a low impurity concentration, formed in the surface region of the semiconductor substrate, and hence two low impurity concentration regions are formed. The source and drain regions respectively consist of a low impurity concentration region and a high impurity concentration region adjacent thereto. The low impurity concentration region allows remarkable improvement of a drain breakdown voltage.