Patent ID: 8643094
Filing Date: 2014-02-04
Classification: H01L

Abstract:
1. A method of forming a MOSFET, comprising the steps of: a1. forming a first trench gate in a semiconductor substrate of a first conductive type, wherein the first trench gate comprises a first projecting portion higher than the top surface of the semiconductor substrate, wherein the first projecting portion has a first sidewall and a second sidewall; a2. forming a second trench gate in the semiconductor substrate, wherein the second trench gate comprises a second projecting portion higher than the top surface of the semiconductor substrate, wherein the second projecting portion has a third sidewall and a fourth sidewall, wherein the second sidewall and the third sidewall are between the first sidewall and the fourth sidewall; a3. forming a first contact opening between the first projecting portion and the second projecting portion, comprising the steps of: a4. implanting first impurities of a second conductivity type to form a body region between the trench gates in the semiconductor substrate, wherein the second conductive type is opposite to the first conductive type; a5. implanting second impurities of a third conductivity type to form a source region over the body region between the trench gates in the semiconductor substrate, wherein the third conductive type is opposite to the second conductive type; and a6. forming a trench in the source region through the first contact opening to separate the source region into two disjoint portions, wherein the bottom of the trench is formed by the body region and is substantially aligned with the bottom of the source region by utilizing a relatively higher etching selectivity of the source region to the L-type shapes.