Nonvolatile semiconductor memory device

A nonvolatile semiconductor memory device, comprising:

• a p-type semiconductor substrate;
• a first active low-density n-type impurity region formed in said semiconductor substrate;
• a second active high-density n-type impurity region formed at one side of said first active region;
• a third active high-density n-type impurity region formed at an opposite side of said first active region;
• a fourth active high-density p-type impurity region formed so as to surround said third active region but not said second active region;
• a first insulating layer overlying said first active region;
• a floating gate on top of said first insulating layer;
• a second insulating layer overlying said floating gate;
• and
• a control gate on top of said second insulating layer.

A nonvolatile semiconductor memory device, comprising:

• a p-type semiconductor substrate;
• a first active low-density n-type impurity region formed in said semiconductor substrate;
• a second active high-density n-type impurity region formed at one side of said first active region;
• a third active high-density n-type impurity region formed at an opposite side of said first active region;
• a fourth active high-density p-type impurity region formed so as to surround said third active region;
• a first insulating layer overlying said first active region;
• a floating gate on top of said first insulating layer;
• a second insulating layer overlying said floating gate;
• a control gate on top of said second insulating layer;
• and
• a fifth active low-density p-type region surrounding said fourth active region, and said first active region surrounds said second active region.

A nonvolatile semiconductor memory device, comprising:

• a p-type semiconductor substrate;
• a first active low-density n-type impurity region formed in said semiconductor substrate;
• a second active high-density n-type impurity region formed at one side of said first active region;
• a third active-high density n-type region formed at an opposite side of said first active region;
• wherein said first active region is deeper than said second and third active regions;
• a fourth active high-density p-type impurity region formed so as to surround said third active region;
• a first insulating layer overlying said first active region;
• a floating gate on top of said first insulating layer;
• a second insulating layer overlying said floating gate;
• and
• a control gate on top of said second insulating layer.

A nonvolatile semiconductor memory device, comprising:

• a p-type semiconductor substrate;
• a first active low-density n-type impurity region formed in said semiconductor substrate;
• a second active high-density n-type impurity region formed at one side of said first active region;
• wherein said first active region surrounds said second active region;
• a third active high-density n-type impurity region formed at an opposite side of said first active region;
• a fourth active high-density p-type impurity region formed so as to surround said third active region;
• a first insulating layer overlying said first active region;
• a floating gate on top of said first insulating layer;
• a second insulating layer overlying said floating gate;
• and
• a control gate on top of said second insulating layer.

A nonvolatile semiconductor device, comprising:

• a p-type semiconductor substrate;
• a first active low-density n-type impurity region formed in said semiconductor substrate;
• a second active high-density n-type impurity region formed at one side of said first active region;
• a third active high-density n-type impurity region formed at an opposite side of said first active region;
• a fourth active high-density p-type impurity region formed so as to surround said third active region;
• a first insulating layer overlying said first active region;
• a floating gate on top of said first insulating layer;
• a second insulating layer overlying said floating gate;
• a control gate on top of said second insulating layer;
• and
• a fifth active low-density p-type impurity region surrounding said fourth active region.