An LDMOSFET is formed at a main surface of a semiconductor substrate. The LDMOSFET includes an n-type drain region, an n-type source region, an n-type drift region, a first p-type well region, and a second p-type well region, all formed in an n-type semiconductor layer. The n-type drift region is in contact with a bottom surface of the n-type drain region, the second p-type well region is in contact with a bottom surface of the n-type source region, and the first p-type well region is in contact with a bottom surface of the n-type drift region and a bottom surface of the second p-type well region. A p-type impurity concentration in the first p-type well region is lower than a p-type impurity concentration in the second p-type well region and is lower than an n-type impurity concentration in the n-type semiconductor layer.