Method of forming insulated gate effect transistor in a substrate depression

Claim 1

A method of forming a semiconductor device having at least one insulated gate field effect transistor comprising the sequential steps of: forming a depression in a surface of a semiconductor substrate, said depression having a bottom surface and at least one side surface to become a channel of said transistor; forming a pair of lightly doped regions in an upper portion of the semiconductor substrate and the bottom surface of the depression; forming a gate insulating layer on said side surface; forming a gate electrode adjacent to said side surface with said gate insulating layer therebetween; and using said gate electrode as a mask to introduce a dopant species to an upper portion of said pair of lightly doped regions in order to form a first heavily doped region in the upper portion of the lightly doped region in the upper portion of the semiconductor substrate and a second heavily doped region in the upper portion of the lightly doped region in the bottom surface of the depression where said first and second heavily doped regions contain said dopant species at a higher concentration than the lightly doped regions which remain after the upper portions thereof have introduced therein said dopant species.

Claim 2

A method of forming a semiconductor device having at least one insulated gate field effect transistor comprising the sequential steps of: forming a depression in a surface of a semiconductor substrate, said depression having a bottom surface and at least one side surface to become a channel of said transistor; forming a pair of lightly doped regions in an upper portion of the semiconductor substrate and the bottom surface of the depression; forming a gate insulating layer on said side surface; forming a gate electrode adjacent to said side surface with said gate insulating layer therebetween; and using said gate electrode as a mask to introduce a dopant species to an upper portion of said pair of lightly doped regions in order to form a first heavily doped region in the upper portion of the lightly doped region in the upper portion of the semiconductor substrate and a second heavily doped region in the upper portion of the lightly doped region in the bottom surface of the depression where said first and second heavily doped regions contain said dopant species at a higher concentration than the lightly doped regions which remain after the upper portions thereof have introduced therein said dopant species.

Claim 11

A method of forming a semiconductor device having at least one insulated gate field effect transistor comprising the sequential steps of: forming a depression in a surface of a semiconductor substrate, the depression having a bottom surface and at least one side surface forming a channel; forming a pair of lightly doped regions in an upper portion of the semiconductor substrate and the bottom surface of the depression; forming a gate insulating layer on the side surface; forming a gate electrode adjacent to the side surface with the gate insulating layer therebetween; and using the gate electrode as a mask, to introduce an impurity to an upper portion of the lightly doped regions in order to form a first heavily doped region in the upper portion of the semiconductor substrate and a second heavily doped region in the upper portion of the lightly doped region in the bottom surface of the depression, wherein the first and second heavily doped regions include the impurity at a higher concentration than the lightly doped regions which remain after the impurity have introduced.

Claim 12

A method of forming a semiconductor device having at least one insulated gate field effect transistor comprising the sequential steps of: forming a depression in a surface of a semiconductor substrate, the depression having a bottom surface and at least one side surface forming a channel; forming a pair of lightly doped regions in an upper portion of the semiconductor substrate and the bottom surface of the depression; forming a gate insulating layer on the side surface; forming a gate electrode adjacent to the side surface with the gate insulating layer therebetween; and using the gate electrode as a mask, to introduce an impurity to an upper portion of the lightly doped regions in order to form a first heavily doped region in the upper portion of the semiconductor substrate and a second heavily doped region in the upper portion of the lightly doped region in the bottom surface of the depression, wherein the first and second heavily doped regions include the impurity at a higher concentration than the lightly doped regions which remain after the impurity have introduced.