Method of producing an LDMOS transistor having reduced dimensions, reduced leakage, and a reduced propensity to latch-up

Claim 1

A method of forming an LDMOS transistor on a substrate of a first conductivity type, comprises the following steps: (a) forming field oxide on said substrate to define an active region of said LDMOS transistor and forming a floating region insulator on an floating region of the active region; (b) forming a gate for said LDMOS transistor at a location near the floating region insulator; (c) implanting impurities of said first conductivity type into said first conductivity type substrate to form a first region of the first conductivity type and a second region of the first conductivity type, the first region of the first conductivity type forming a drain for said LDMOS transistor; (d) forming a first trench in the second region of the first conductivity type to define residual portions of second region of the first conductivity type as a source for said LDMOS transistor; (e) forming a second trench on the first trench, the second trench being formed in a direction from the first trench into the substrate, the second trench having at least two planes; (f) implanting and diffusing impurities of a second conductivity type into the second trench to form a body region of the second conductivity type, the body region of the second type enclosing the source; and (g) forming drain and source contacts on said drain and source, respectively.

Claim 2

A method of forming an LDMOS transistor on a substrate of a first conductivity type, comprises the following steps: (a) forming field oxide on said substrate to define an active region of said LDMOS transistor and forming a floating region insulator on an floating region of the active region; (b) forming a gate for said LDMOS transistor at a location near the floating region insulator; (c) implanting impurities of said first conductivity type into said first conductivity type substrate to form a first region of the first conductivity type and a second region of the first conductivity type, the first region of the first conductivity type forming a drain for said LDMOS transistor; (d) forming a first trench in the second region of the first conductivity type to define residual portions of second region of the first conductivity type as a source for said LDMOS transistor; (e) forming a second trench on the first trench, the second trench being formed in a direction from the first trench into the substrate, the second trench having at least two planes; (f) implanting and diffusing impurities of a second conductivity type into the second trench to form a body region of the second conductivity type, the body region of the second type enclosing the source; and (g) forming drain and source contacts on said drain and source, respectively.