A variable capacitor includes an N+ layer including a variable capacitance region, a P+ layer epitaxially grown on the N+ layer and formed from a SiGe film and a Si film, and a P-type electrode. An NPN-HBT (Hetero-junction Bipolar Transistor) includes a collector diffusion layer formed simultaneously with the N+ layer of the variable capacitor, a collector layer, and a Si/SiGe layer epitaxially grown simultaneously with the P+ layer of the variable capacitor. Since a depletion layer formed in a PN junction of the variable capacitor can extend entirely across the N+ layer, reduction in variation range of the capacitance can be suppressed.