An exemplary nitride-based semiconductor device includes: a semiconductor multilayer structure 20 which includes a p-type semiconductor region with a surface 12 being inclined from the m-plane by an angle of not less than 1° and not more than 5° or the principal surface has a plurality of m-plane steps; and an electrode 30 provided on the p-type semiconductor region. The p-type semiconductor region is formed by an AlxInyGazN (where x+y+z=1, x≧0, y≧0, and z>0) layer 26. The electrode 30 includes a Zn layer 32 and a Ag layer 34 provided on the Zn layer 32. The Zn layer is in contact with the surface 12 of the p-type semiconductor region of the semiconductor multilayer structure 20.