Method for preparing a high mobility, lightly-doped channel mis-type FET with reduced latch up and punchthrough

摘要

A method for preparing a MISFET of a minute size with the channel length of not more than 2 mu m between a source and a drain, comprises the steps of forming a mask for exposing a region for forming a well on a planar surface of a semiconductor substrate, and introducing ions at a predetermined energy into the well region by using the mask. The predetermined energy is such as to form a peak of the impurity concentration distribution at a position deeper than the bottom surface of the source and the drain and to maintain the layer of at least a partial layer of the channel at an impurity concentration lower than 1016 cm-3 so that a high speed carrier movement in the channel is provided without causing a punch-through phenomenon.