Semiconductor device production method and semiconductor device

A semiconductor device production method comprising:

• forming an element-separating insulation film in a semiconductor substrate to define a semiconductor region that includes a first region, a second region connecting with the first region and having a width smaller than a width of the first region, and a third region connecting with the second region and having a width smaller than the width of the second region;
• implanting a first conductivity type impurity into the semiconductor region to form a well region;
• forming a gate insulation film on the well region;
• forming, on the gate insulation film, a gate electrode that includes a first part crossing the third region in width direction of the third region and a second part extending from the first part across the second region and the first region;
• forming a side wall insulation film on a side wall of the gate electrode, in the second region, the side wall insulation film covering a part of the second region while exposing a remaining part of the second region;
• implanting a second conductivity type impurity that has a conductivity type opposite to the first conductivity type into the first region and the second region using the gate electrode and the side wall insulation film as a mask, to form a source region and a drain region in the first region and the second region on both sides of the second part of the gate electrode;
• performing heat treatment to diffuse the second conductivity type impurity;
• removing partial thickness of the side wall insulation film;
• and
• forming a silicide layer on the first region and the second region after the removing the partial thickness of the side wall insulation film.