|Summary:||碩士 === 國立中央大學 === 產業經濟研究所在職專班 === 104 === The competition faced by technology industry in Taiwan is tough now. Taking firms in semiconductor industry for example, they execute R&D in the production process or product innovation to enhance the competitive advantage. Therefore, from the viewpoint of the commodity cycle, we can see the firm who has been a monopolist will face an oligopolistic market when there appears other competitor. In order to analyze vendor market behavior clearly, we refer to D’Aspremont and Jacqumin (1988) but consider the market to be Bertrand price competition or Stackelberg quantity competition to build new models to investigate the impact of the R&D spillover effect on firms’ R&D strategies. We have the following four findings. First, under Bertrand competition, when market is more competitive, the more R&D investments the firms will invest. Second, under Bertrand competition, when the product is more similar, the possibility of cooperation in R&D by the two firms is smaller. Third, under Stackelberg competition, the leading firm will invest more R&D than the follower. Fourth, under Stackelberg competition, whatever the scale of the spillover effect, the leader will not cooperate to execute R&D.