The semiconductor device comprises a first well 14 of a first conduction type formed in a semiconductor substrate 10; a second well 16 of a second conduction type formed in the first well 14; and a transistor 40 including a control gate 18 formed of an impurity region of the first conduction type formed in the second well 16, a first impurity diffused layer 26 and a second impurity diffused layer 33 formed with a channel region 25 therebetween, and a floating gate electrode 20 formed on the channel region 25 and the control gate 18 with a gate insulation film 24 therebetween. The control gate 18 is buried in the semiconductor substrate 10, which makes it unnecessary to form the control gate 18 on the floating gate electrode 20. Thus, the memory transistor and the other transistors, etc. can be formed by the same fabricating process. Thus, the fabrication processes can be less and the semiconductor device can be inexpensive.