A semiconductor device (21) can include, e.g., a recessed portion (25) on the reverse surface (224) of an insulating resin (22) which is the mounting surface of the semiconductor device (21). Additionally, on the outer peripheral surface of the recessed portion (25), the exposed region of leads (26) and the reverse surface (224) of the insulating resin (22) form generally the same plane. This allows, e.g., a QFN semiconductor device (21) according to preferred embodiments herein to place dust particles in the recessed portion (25) even in the presence of dust particles such as crushed burr particles of the leads (26) or plastic burrs, thereby avoiding mounting deficiencies when mounting the semiconductor device.