The present invention provides a semiconductor device having a well, formed in a semiconductor substrate by using a mask in which a mask pattern width of a portion corresponding to an opening diameter is equal to or less than twice the diffusion depth of the well layer, and a gate electrode formed to...http://www.google.com/patents/US5210437?utm_source=gb-gplus-sharePatent US5210437 - MOS device having a well layer for controlling threshold voltage
