Asymmetric transistor and its manufacture

PROBLEM TO BE SOLVED: To provide a transistor, in which a short channel effect is reduced, and its manufacture. SOLUTION: A transistor 10 has first conductivity type source region 20 and drain region 22 formed in a substrate 12. The transistor 10 also comprises a second conductivity type asymmetical channel region 24 formed in the substrate 1 between the source region 20 and the drain region 22. The asymmetrical channel region 24 has second conductivity type dopant concentration at a place adjacent to the source region 20 lower than the dopant concentration at a place adjacent to the drain region 22.