Semiconductor devices with non-punch-through semiconductor channels having enhanced conduction and methods of making

A method of making a semiconductor device comprising:

• selectively etching through a third layer of a semiconductor material of a first conductivity type, wherein the third layer is on a second layer of a semiconductor material of the first conductivity type and wherein the second layer is on a first layer of a semiconductor material of the first conductivity type and wherein the first layer is on a substrate layer of a semiconductor material of the first conductivity type, wherein selectively etching through the third layer comprises selectively etching into the underlying second layer to form a raised region of semiconductor material of the first conductivity type having an upper surface comprising semiconductor material of the third layer and tapered sidewalls comprising semiconductor material of the second layer;
• selectively implanting dopants into the semiconductor material of the second layer on the sidewalls of the raised region and on etched surfaces of the second layer adjacent to the raised region to form regions of semiconductor material of a second conductivity type different than the first conductivity type on the sidewalls of the raised region and on the etched surfaces of the second layer adjacent to the raised region;
• wherein the second layer comprises a first portion with a first average dopant concentration adjacent the third layer and a second portion with a second average dopant concentration between the first portion and the first layer, wherein the first average dopant concentration is lower than the second average dopant concentration and wherein the second average dopant concentration is higher than the average dopant concentration of the first layer.