Use of mask shadowing and angled implantation in fabricating asymmetrical field-effect transistors

A method comprising the steps of:

• furnishing primary and additional gate electrodes for respective primary and additional like-polarity field-effect transistors above, and vertically separated by gate dielectric material from, respective laterally separated primary and additional intended channel-zone locations in a semiconductor body along its upper surface;
• providing a mask over the semiconductor body and the gate electrodes such that the mask has at least one mask opening which at least partially overlies the gate electrodes, which defines opposite first and second primary transverse mask sides located laterally beyond the primary gate electrode and any material situated on opposite transverse sides of the primary gate electrode, and which defines opposite first and second additional transverse mask sides located laterally beyond the gate electrode and any material situated on opposite transverse sides of the additional gate electrode;
• and
• directing first ions of a species of a primary semiconductor dopant toward the mask and each mask opening at a first average tilt angle of at least 15° along paths that originate laterally beyond the two first transverse mask sides such that an electrically significant amount of the first ions passes through one such mask opening and enters the primary channel-zone location and such that the mask, the additional gate electrode, and any material situated along the additional gate electrode substantially block any electrically significant amount of the first ions from entering the additional channel-zone location, the first tilt angle being measured from a perpendicular to a plane extending generally along the semiconductor body's upper surface.

A method comprising the steps of:

• furnishing primary and additional gate electrodes for respective primary and additional like-polarity field-effect transistors above, and vertically separated by gate dielectric material from, respective laterally separated primary and additional intended channel-zone locations in a semiconductor body along its upper surface, the two channel-zone locations having respective substantially parallel channel-length directions;
• providing a mask over the semiconductor body and the gate electrodes such that the mask has at least one mask opening which at least partially overlies the gate electrodes, which defines opposite first and second primary transverse mask sides located laterally beyond the primary gate electrode and any material situated on opposite transverse sides of the primary gate electrode, and which defines opposite first and second additional transverse mask sides located laterally beyond the gate electrode and any material situated on opposite transverse sides of the additional gate electrode;
• and
• directing first ions of a species of a primary semiconductor dopant toward the mask and each mask opening at a first average tilt angle of at least 15° along paths that originate laterally beyond the two first transverse mask sides such that an electrically significant amount of the first ions passes through one such mask opening and enters the primary channel-zone location and such that the mask, the additional gate electrode, and any material situated along the additional gate electrode substantially block any electrically significant amount of the first ions from entering the additional channel-zone location, the first tilt angle being measured from a perpendicular to a plane extending generally along the semiconductor body's upper surface.