A semiconductor device having sense amplifiers and methods for their preparation

There is provided a semiconductor device which avoids the reduction of the scanning speeds of several sense amplifiers because of their control systems. In the semiconductor device (3) is arranged selectively a P-well layer (6) on a main surface of an epitaxial layer containing p-type impurity. It is an N-bottom layer (7) contains the N-type impurity, is arranged which communicates with a bottom of the P-well layer (6) in contact. A P-well layer (2) is arranged with a thickness such that it is in contact with the N-bottom layer (7), so that the N-bottom layer (7) and the P-well layer (2) forming a PN junction , Furthermore, are provided at the main surface of the epitaxial layer (3) selectively an N-well layer (4) containing N-type impurity, and a P-well layer (5) contains the P-type impurities disposed so that the P-well layer (6 ) is located between them.