Method of making V-MOS field effect transistors utilizing a two-step anisotropic etching and ion implantation

Claim 1

A method of making a V-MOS field effect transistor comprising the steps of: forming a masking layer over a surface of a crystalline substrate; opening an aperture in said masking layer to expose said surface of said substrate; applying an anisotropic etchant to said exposed surface to etch a groove in said crystalline substrate, said groove having a decreasing width with increasing depth; inhibiting the effect of said anisotropic etchant before the etch goes to completion so that a V-shaped groove is only partially formed; accelerating ions through said aperture for implantation in said crystalline substrate in the lower portion of the partially formed V-shaped groove; and thereafter reapplying an anisotropic etchant to said partially formed V-shaped groove and allowing the etch to go to completion.

Claim 2

A method of making a V-MOS field effect transistor comprising the steps of: forming a masking layer over a surface of a crystalline substrate; opening an aperture in said masking layer to expose said surface of said substrate; applying an anisotropic etchant to said exposed surface to etch a groove in said crystalline substrate, said groove having a decreasing width with increasing depth; inhibiting the effect of said anisotropic etchant before the etch goes to completion so that a V-shaped groove is only partially formed; accelerating ions through said aperture for implantation in said crystalline substrate in the lower portion of the partially formed V-shaped groove; and thereafter reapplying an anisotropic etchant to said partially formed V-shaped groove and allowing the etch to go to completion.

Claim 4

The method of making a V-MOS field effect transistor comprising the steps of: forming a masking layer over a surface of a crystalline substrate of one conductivity type; opening a first aperture in said masking layer to expose said surface of said substrate; forming a region of a second conductivity type in said substrate through said first aperture; forming an oxide layer over the exposed surface of said substrate to cover said region of said second conductivity type; thereafter opening a second aperture in said oxide layer to expose a surface over said region of said second conductivity type, said second aperture being smaller than said first aperture; applying an anisotropic etchant to said exposed surface over said region of said second conductivity type to etch a groove in said crystalline substrate, said groove having a decreasing width with increasing depth; inhibiting the effect of said anisotropic etchant before the etch goes to completion so that a V-shaped groove is only partially formed, the partially formed V-shaped groove penetrating said region of said second conductivity type and dividing it into two parts; accelerating ions through said second aperture for implantation in said crystalline substrate in the lower portion of the partially formed V-shaped groove, said ions forming a bridging diffusion region of said second conductivity type connecting the two parts of the region divided by said partially formed V-shaped groove; and thereafter reapplying an anisotropic etchant to said partially formed V-shaped groove and allowing the etch to go to completion, the completed V-shaped groove penetrating said bridging region.

Claim 5

The method of making a V-MOS field effect transistor comprising the steps of: forming a masking layer over a surface of a crystalline substrate of one conductivity type; opening a first aperture in said masking layer to expose said surface of said substrate; forming a region of a second conductivity type in said substrate through said first aperture; forming an oxide layer over the exposed surface of said substrate to cover said region of said second conductivity type; thereafter opening a second aperture in said oxide layer to expose a surface over said region of said second conductivity type, said second aperture being smaller than said first aperture; applying an anisotropic etchant to said exposed surface over said region of said second conductivity type to etch a groove in said crystalline substrate, said groove having a decreasing width with increasing depth; inhibiting the effect of said anisotropic etchant before the etch goes to completion so that a V-shaped groove is only partially formed, the partially formed V-shaped groove penetrating said region of said second conductivity type and dividing it into two parts; accelerating ions through said second aperture for implantation in said crystalline substrate in the lower portion of the partially formed V-shaped groove, said ions forming a bridging diffusion region of said second conductivity type connecting the two parts of the region divided by said partially formed V-shaped groove; and thereafter reapplying an anisotropic etchant to said partially formed V-shaped groove and allowing the etch to go to completion, the completed V-shaped groove penetrating said bridging region.