Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a first conductivity type semiconductor substrate;
• a second conductivity type first buried diffusion layer and a second conductivity type second buried diffusion layer that are arranged in the semiconductor substrate;
• a semiconductor layer arranged on the semiconductor substrate;
• a second conductivity type first impurity diffusion region that is arranged in the semiconductor layer and surrounds a first region of the semiconductor layer on the first buried diffusion layer in plan view;
• a second conductivity type second impurity diffusion region that is arranged, in the semiconductor layer, on the second buried diffusion layer;
• a second conductivity type first well that is arranged in the first region of the semiconductor layer;
• a first conductivity type second well that is arranged, in the semiconductor layer, in a second region that is in contact with the second impurity diffusion region;
• a first conductivity type third impurity diffusion region and a first conductivity type fourth impurity diffusion region that are arranged in the first well;
• and
• a first conductivity type fifth impurity diffusion region that is arranged in the second well, wherein
• the first conductivity type semiconductor substrate, the second conductivity type first buried diffusion layer, the semiconductor layer, the second conductivity type first impurity diffusion region, the second conductivity type first well, the first conductivity type third impurity diffusion region and the first conductivity type fourth impurity diffusion region form a lateral bipolar transistor, and
• the first conductivity type semiconductor substrate, the second conductivity type second buried diffusion layer, the semiconductor layer, the second conductivity type second impurity diffusion region, the first conductivity type second well, and the first conductivity type fifth impurity diffusion region form a lateral zener diode.