In a deep trench DTC reaching a predetermined depth from a first main surface of a semiconductor substrate SUB, a plurality of columnar conductors CCB including plugs PUG and field plates FP are formed. A p type impurity layer PIL is formed along the side wall surface of the deep trench DTC. Between the bottom of the plug PUG and the bottom of the p type impurity layer PIL, the field plate FP and the p type impurity layer PIL are positioned to face each other via an insulating film FIF interposed therebetween. Between the bottom of the p type impurity layer PIL and the bottom of the field plate FP, the field plate FP and an n-type drift layer NDL of the semiconductor substrate SUB are positioned to face each other via the insulating film FIF interposed therebetween.