Non-volatile semiconductor memory device and method of manufacturing the same

A method of manufacturing a nonvolatile semiconductor memory device comprising the steps of:

• (a) forming a first semiconductor region of a first conductivity type constituting a well on a main surface of a semiconductor substrate having a first direction and a second direction intersecting the first direction;
• (b) forming a gate conductive film to constitute a gate on the main surface of the semiconductor substrate interposing an insulating film, and patterning the gate conductive film so as to extend in the first direction after the step (a);
• (c) forming a second semiconductor region of a second conductivity type opposite the first conductivity type constituting a drain in the first semiconductor region under one side of sidewalls of the gate after the step (b);
• (d) forming a third semiconductor region of the second conductivity type constituting a source in the first semiconductor region under another side of the sidewalls of the gate after the step (b);
• (e) forming a hole penetrating through the third semiconductor region after the step (d);
• and
• (f) a step of burying a metal film in the hole to form a contact electrically connected to the third semiconductor region and the first semiconductor region,
• wherein,
• between the step (a) and the step (b), a plurality of isolations extending in the second direction are formed along the first direction and deeper than the first semiconductor region on the main surface of the semiconductor substrate,
• after the step (c), a wiring conductive film to constitute a data line is formed on the main surface of the semiconductor substrate, and the wiring conductive film is patterned so as to extend in the first direction on the second semiconductor region and the isolation,
• after step (a) and before step (d), a fourth semiconductor region of the first conductivity type whose impurity density is higher than that of the first semiconductor region is formed in the first semiconductor region, and
• the hole reaches the fourth semiconductor region.