Method of manufacturing semiconductor device with retrograde wells

A method of manufacturing a semiconductor memory device including a memory cell array region and a peripheral circuit region, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an isolation insulating film having a thickness to isolate an element formation region included in said memory cell array region and said peripheral circuit region;
• implanting an impurity into a region of said semiconductor substrate from above the main surface of said semiconductor substrate through said isolation insulating film, thereby forming a well region having an impurity concentration distribution in the region of said semiconductor substrate positioned under said isolation insulating film;
• and subsequently
• selectively removing the surface portion of the isolation insulating film positioned in said memory cell array region so that the thickness of the isolation insulating film in said memory cell array region is reduced.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an isolation insulating film to isolate an element formation region;
• forming a mask layer to expose a surface of said isolation insulating film;
• implanting an impurity, in a first implanting step, through said exposed isolation insulating film, thereby forming a first impurity region in a region in said semiconductor substrate;
• implanting a second impurity, in a second implantation step at a greater implantation energy than the first implantation step, in a region at a greater distance from the surface of said semiconductor substrate than said first impurity region from above the main surface of said semiconductor substrate;
• and
• removing a surface portion of said isolation insulating film after forming said well region so that the top surface of the peripheral portion of the isolation insulating film is positioned below the main surface of the semiconductor substrate.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an isolation insulating film to isolate an element formation region;
• forming a mask layer to expose a surface of said isolation insulating film;
• implanting an impurity, in a first implanting step, through said exposed isolation insulating film, thereby forming a first impurity region in a region in said semiconductor substrate;
• and
• implanting a second impurity, in a second implantation step at a greater implantation energy than the first implantation step, in a region at a greater distance from the surface of said semiconductor substrate than said first impurity region from above the main surface of said semiconductor substrate, wherein
• said first impurity region has a first impurity concentration peak portion,
• said second impurity region has a second impurity concentration peak portion, and a third impurity concentration peak portion under the second impurity concentration peak portion, and
• said first impurity concentration peak portion and said second impurity concentration peak portion are formed individually without a shared portion.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an element isolation layer to isolate an element formation region;
• forming on said element isolation layer a mask layer to expose a surface of said element formation region;
• implanting an impurity through said mask layer and said element isolation layer, thereby forming an impurity region extending from a first region in said semiconductor substrate to a second region at a greater distance from the surface of said semiconductor substrate than the first region;
• wherein
• said mask layer is formed to cover the entire upper surface of said element isolation layer.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an element isolation layer to isolate an element formation region;
• forming on said element isolation layer a mask layer to expose a surface of said element formation region;
• implanting an impurity through said mask layer and said element isolation layer, thereby forming an impurity region extending from a first region in said semiconductor substrate to a second region at a greater distance from the surface of said semiconductor substrate than the first region;
• wherein
• said step of forming the element isolation layer includes the steps of:
• forming on said main surface of said semiconductor substrate an oxide film having a thickness by CVD;
• and
• patterning said oxide film, thereby leaving said oxide film in the element isolation region, and wherein
• said impurity region has a first impurity concentration peak portion, and a second impurity concentration peak portion under the first impurity concentration peak portion,
• said first impurity concentration peak portion is formed by implanting said impurity through said oxide film and said mask layer before said oxide film is patterned, and then said oxide film is patterned using said mask layer as a mask.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an element isolation layer to isolate an element formation region;
• forming on said element isolation layer a mask layer to expose a surface of said element formation region;
• implanting an impurity through said mask layer and said element isolation layer, thereby forming an impurity region extending from a first region in said semiconductor substrate to a second region at a greater distance from the surface of said semiconductor substrate than the first region, wherein
• said element isolation layer includes a stacked layer structure formed of an insulating layer formed on said semiconductor substrate and a conductive layer formed on the insulating layer.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively forming on a main surface of a semiconductor substrate an element isolation layer to isolate an element formation region;
• forming on said element isolation layer a mask layer to expose a surface of said element formation region;
• implanting an impurity through said mask layer and said element isolation layer, thereby forming an impurity region extending from a first region in said semiconductor substrate to a second region at a greater distance from the surface of said semiconductor substrate than the first region, wherein
• an insulating layer and a conductive layer constituting said element isolation layer are formed in turn on the entire main surface of said semiconductor substrate,
• a mask layer is patterned on said conductive layer, and
• said element isolation layer is left on the element isolation region by performing etching using said mask layer as mask.

A method of manufacturing a semiconductor device, comprising the steps of:

• selectively implanting an impurity into a first region in an element isolation region of a semiconductor substrate;
• forming on a main surface of said semiconductor substrate an isolation insulating film having a thickness in a second region including and surrounding said first region in said element isolation region, thereby forming a first impurity region in said first region;
• and
• forming a second impurity region from above the main surface of said semiconductor substrate in a region further away from the surface of said semiconductor substrate than said first impurity region.