Method of threshold voltage control in metal-oxide-semiconductor devices

A method of manufacturing a complimentary metal-oxide-semiconductor (CMOS) circuit including a number of devices on a semiconductor substrate of a first conductivity type, the method comprising:

• forming a first photoresist mask on a surface of the substrate using a photolithographic process from a reticule having a drawn well boundary, the first photoresist mask defining a well boundary around an area in which a well is to be formed;
• implanting ions into the substrate at an angle substantially perpendicular to the surface of the substrate to form a well of a second conductivity type in the substrate, wherein a region proximal to the well boundary which is effected by lateral scattering by the first photoresist mask of the ions implanted to form the well;
• forming at least one of the devices in the region proximal to the well boundary which is effected by lateral scattering, wherein a channel of the device is formed by implanting ions into the substrate at an acute angle to the surface thereof to shadow the portion of the channel from at least some of the ions implanted to form the channel;
• and
• wherein the location of the drawn well boundary and the acute angle at which ions are implanted into the substrate to form the channel are selected to control threshold voltages (VT) of devices in the circuit proximal to the well boundary.