A method for manufacturing a CMOS transistor includes preparing a silicon substrate provided with a first buried layer, a second buried layer and a body, vertically forming device-isolation films inside the body, forming a first-type well inside the body arranged on the first buried layer, and vertically forming a first source and drain region inside the first-type well, forming a second-type well inside the body arranged on the second buried layer, and vertically forming a second source and drain region inside the second-type well, and vertically forming a recessed gate between the first-type well and the second-type well.