Semiconductor Device and Its Manufacturing Method

A method of manufacturing a semiconductor device including a semiconductor substrate and a MOS transistor formed on the semiconductor substrate, the method comprising:

• preparing the semiconductor substrate;
• forming a semiconductor layer of a first conduction type on the semiconductor substrate;
• forming an element isolation film on the semiconductor layer;
• forming a gate oxide film of the MOS transistor;
• forming a gate electrode of the MOS transistor on the gate oxide film such that the gate electrode has a part extending up onto the element isolation film;
• forming a body region of a second conduction type opposite to the first conduction type;
• and
• forming a short channel region of the first conduction type on the semiconductor layer,
• wherein the method further includes:
• forming a source region of the first conduction type and a drain region of the conduction type such that the source region and the drain region are isolated from each other by the element isolation film, and
• wherein the step of forming the short channel region is performed after the step of forming the gate oxide film.