Semiconductor device including impurity layer having continuous portions formed at different depths and method of manufacturing the same

摘要

A trench is formed in a substrate and a silicon oxide film which serves as a trench isolation is buried in the trench. The silicon oxide film has no shape sagging from a main surface of the substrate. A channel impurity layer to control a threshold voltage of a MOSFET is formed in the main surface of the substrate. The channel impurity layer is made of P-type layer, having an impurity concentration higher than that of the substrate. A first portion of the channel impurity layer is formed near an opening edge of the trench along a side surface of the trench in the source/drain layer, and more specifically, in the N+-type layer. A second portion of the channel impurity layer is formed deeper than the first portion. A gate insulating film and a gate electrode are formed on the main surface of the substrate.