Abstract: A method is proposed for manufacturing a semiconductor device, which comprises forming groove(s) having a vertical wall in a semiconductor substrate; doping the same type of impurity as that of the substrate at a dose of not less than 1.times.10.sup.14 cm.sup.-2 or the opposite type of impurity to that of the substrate in said groove(s) to form an impurity region; filling the groove(s) with an insulating material to form a field region. A semiconductor device having an impurity region of the same conductivity type as that of the semiconductor substrate under a buried field region and of a sheet resistance .rho.s=50 ohms/.quadrature. is also proposed.