A resin-encapsulated semiconductor device having a semiconductor chip which is prevented from being damaged. The resin-encapsulated semiconductor device (100) comprises a semiconductor chip (1) including a silicon substrate, a die pad (10) to which the semiconductor chip (1) is secured through a first solder layer (2), a resin-encapsulating layer (30) encapsulating the semiconductor chip (1), and lead terminals (21) electrically connected to the semiconductor chip (1) and including inner lead portion (21b) covered with the resin-encapsulating layer (30). The lead terminals (21) are made of copper or a copper alloy. The die pad (10) is made of 42 alloy or a cover alloy and has a thickness (about 0.125 mm) less than the thickness (about 0.15 mm) of the lead terminals (21).